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[Millisman]

GPL-2.0
Open Access: If you distribute software under the GPL, you must make the source code available.
Derivative Works: Any modifications or derivative works of the GPL code must also be distributed under the open source GPL license.
Transfer of Rights: Users are given the freedom to study, change, and distribute the code.
Preservation of Freedom: The purpose of the GPL is to ensure that free software remains free.
Versions: There are different versions of the GPL (e.g. GPLv2, GPLv3), but they all require the source code to be made available.