relicense under spdx identifier MIT OR (Apache-2.0 WITH LLVM-exception)

[TheButlah]

Rebased on #2, merge that one first.

This PR relicenses the code as MIT OR (Apache-2.0 WITH LLVM-exception). The new license files are located at LICENSE-MIT and LICENSE-APACHE.

Rationale of license choice

The reason why Apache-2.0 WITH LLVM-exception is good:

• unlike normal Apache, it has improved compatibility with GPLv2 libraries.
• It is well established - clang uses this version of apache.
• Unlike MIT, it explicitly grants patent rights to consumers of the code. This protects end users from patent trolls.

The reason why MIT is good:

• Everyone knows it
• Its short
• Its highly permissive

The OR in the license clause means that contributors to the code agree to both licenses. Which means consumers of the code are protected by both, and if one or the other better suits their needs, they can choose which one to consume the library under. It also means that forks of the code could remove one of the two licenses, if they needed to be more compatible with some project (downgrade from dual to single license). This dual licensing strategy is inspired by Rust's licensing scheme. In practice, this means the license is even more permissive than just MIT or just Apache 2.0 would be alone.

This licensing scheme is the same as what we use in other repos, most notably, orb-software.

Contributor agreement

I would like to request that all contributors to this codebase to date comment the following to indicate their agreement with the relicense:

I approve the relicense of all past and future contributions in this repository to the MIT OR (Apache-2.0 WITH LLVM-exception) license. I understand that I am granting patent rights as defined in LICENSE-APACHE, and I understand that the code will be open sourced publicly. I have been authorized by my employer (Modulus Labs) to grant the code under this license.

Contributors that must sign off before this PR can be merged and the relicense completed:

• @vishady721
• @NayrOacModulus
• @giorgos-ml
• @BenModulusLabs

[NayrOacModulus]

I approve the relicense of all past and future contributions in this repository to the MIT OR (Apache-2.0 WITH LLVM-exception) license. I understand that I am granting patent rights as defined in LICENSE-APACHE, and I understand that the code will be open sourced publicly. I have been authorized by my employer (Modulus Labs) to grant the code under this license.

[BenModulusLabs]

I approve the relicense of all past and future contributions in this repository to the MIT OR (Apache-2.0 WITH LLVM-exception) license. I understand that I am granting patent rights as defined in LICENSE-APACHE, and I understand that the code will be open sourced publicly. I have been authorized by my employer (Modulus Labs) to grant the code under this license.

[giorgos-ml]

I approve the relicense of all past and future contributions in this repository to the MIT OR (Apache-2.0 WITH LLVM-exception) license. I understand that I am granting patent rights as defined in LICENSE-APACHE, and I understand that the code will be open sourced publicly. I have been authorized by my employer (Modulus Labs) to grant the code under this license.

[vishady721]

I approve the relicense of all past and future contributions in this repository to the MIT OR (Apache-2.0 WITH LLVM-exception) license. I understand that I am granting patent rights as defined in LICENSE-APACHE, and I understand that the code will be open sourced publicly. I have been authorized by my employer (Modulus Labs) to grant the code under this license.

[TheButlah]

Once @vishady721 approves the PR, it should merge

[vishady721]

yayyyy!