diff --git a/Makefile b/Makefile
index a34bc7b..9caffef 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,21 @@
+# Copyright ©2011 Adrian Kennard
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details. 
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 BIN=./bin/
 LIB=./lib/
+
 ALL=${BIN}e3d
 
 all: ${ALL}
diff --git a/README b/README
index 61dfae9..694953e 100644
--- a/README
+++ b/README
@@ -2,7 +2,15 @@ This is a 3D slicer. It converts STL in to GCODE, and will make SVG for preview.
 I am still tinkering with this, but it basically works.
 RevK on freenode#reprap and @TheRealRevK on twitter
 
-Licencing...
-18:28 < RevK> But it is basically "do what the fuck you like, don't sue me if 
-              it does not work, and tell people I wrote the good bits"
-18:28 < RevK> Which I think is basically GPL
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
diff --git a/e3d-common.c b/e3d-common.c
index 2bc6f51..27dbd81 100644
--- a/e3d-common.c
+++ b/e3d-common.c
@@ -1,5 +1,20 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Common functions
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
 
 #include <stdio.h>
 #include <string.h>
diff --git a/e3d-fill.c b/e3d-fill.c
index fb43e69..d79feb4 100644
--- a/e3d-fill.c
+++ b/e3d-fill.c
@@ -1,5 +1,19 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Make extrude path for each slice
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 
 #include <stdio.h>
 #include <string.h>
diff --git a/e3d-fill.h b/e3d-fill.h
index fdc2bea..a0715de 100644
--- a/e3d-fill.h
+++ b/e3d-fill.h
@@ -1,5 +1,18 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Make extrude path for each slice
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include "e3d.h"
 
diff --git a/e3d-gcode.c b/e3d-gcode.c
index ae91c40..3228504 100644
--- a/e3d-gcode.c
+++ b/e3d-gcode.c
@@ -1,5 +1,19 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Output GCODE
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 
 #include <stdio.h>
 #include <string.h>
diff --git a/e3d-gcode.h b/e3d-gcode.h
index 2a3bc64..52b2c20 100644
--- a/e3d-gcode.h
+++ b/e3d-gcode.h
@@ -1,5 +1,18 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Output GCODE
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include "e3d.h"
 
diff --git a/e3d-slice.c b/e3d-slice.c
index 169f6fc..cf86748 100644
--- a/e3d-slice.c
+++ b/e3d-slice.c
@@ -1,5 +1,19 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // STL processing functions
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 
 #include <stdio.h>
 #include <string.h>
diff --git a/e3d-slice.h b/e3d-slice.h
index 620ef03..466775c 100644
--- a/e3d-slice.h
+++ b/e3d-slice.h
@@ -1,5 +1,19 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Slicing STL
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 
 #include "e3d.h"
 
diff --git a/e3d-stl.c b/e3d-stl.c
index 18ffa72..8f182cc 100644
--- a/e3d-stl.c
+++ b/e3d-stl.c
@@ -1,5 +1,19 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // STL processing functions
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 
 #include <stdio.h>
 #include <string.h>
diff --git a/e3d-stl.h b/e3d-stl.h
index 0ac96f1..ef742b6 100644
--- a/e3d-stl.h
+++ b/e3d-stl.h
@@ -1,5 +1,19 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // STL processing functions
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 
 #include "e3d.h"
 
diff --git a/e3d-svg.c b/e3d-svg.c
index 253e596..4b11580 100644
--- a/e3d-svg.c
+++ b/e3d-svg.c
@@ -1,5 +1,18 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Output SVG
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include <stdio.h>
 #include <string.h>
diff --git a/e3d-svg.h b/e3d-svg.h
index f7c34b3..7eb784e 100644
--- a/e3d-svg.h
+++ b/e3d-svg.h
@@ -1,5 +1,18 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Output SVG
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include "e3d.h"
 
diff --git a/e3d.c b/e3d.c
index 4db5828..927cb1f 100644
--- a/e3d.c
+++ b/e3d.c
@@ -1,6 +1,19 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Processes 3D STL files to make GCODE suitable for extrusion printers
 //
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
 
 #include <stdio.h>
 #include <string.h>
diff --git a/e3d.h b/e3d.h
index 2efacaf..19ae655 100644
--- a/e3d.h
+++ b/e3d.h
@@ -1,5 +1,18 @@
 // Extrude 3D model (e3d) Copyright ©2011 Adrian Kennard
 // Common definitions for all modules
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #ifndef	INCLUDE_E3D
 #define	INCLUDE_E3D
diff --git a/poly.c b/poly.c
index 3267958..8f7497a 100644
--- a/poly.c
+++ b/poly.c
@@ -1,4 +1,18 @@
 // 2D Polygon library Copyright ©2011 Adrian Kennard
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
 
 #include <math.h>
 #include <malloc.h>
diff --git a/poly.h b/poly.h
index b3c6d0f..fde235c 100644
--- a/poly.h
+++ b/poly.h
@@ -1,4 +1,17 @@
 // 2D Polygon library Copyright ©2011 Adrian Kennard
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details. 
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 //#define       POLY_FLOAT      // Define to use float, not recommended