License

[gnzlbg]

Is there a reason this isn't dual-licensed with Apache 2.0 OR MIT ?

[gnzlbg]

I think that isn't 100% necessary, but since this crate is pulled by libstd, it would simplify things if it would support the same licenses as the Rust runtime.

[mati865]

cc rust-lang/rust#63676 which is integrating this crate into libstd.

[sunfishcode]

@gnzlbg No deep reason. I'm fine changing it. Would (Apache-2.0 WITH LLVM-exception) OR MIT be acceptable? It's strictly more permissive than Apache-2.0 OR MIT.

@newpavlov Do you agree to relicensing? If so, please comment with:

I license past and future contributions under the dual (Apache-2.0 WITH LLVM-exception) OR MIT licenses, allowing licensees to chose either at their option.

[newpavlov]

I license past and future contributions under the dual (Apache-2.0 WITH LLVM-exception) OR MIT licenses, allowing licensees to chose either at their option.

But do we really need the LLVM-exception? Shouldn't MIT license already be compatible with LLVM?

[gnzlbg]

Would (Apache-2.0 WITH LLVM-exception) OR MIT be acceptable?

Maybe @brson knows?

I'm not a lawyer, so I really have no idea. Triple-licensing it as "Apache-2.0 WITH LLVM-exception OR Apache-2.0 OR MIT" would probably work though.

[sunfishcode]

I'm also not a lawyer and can't say whether triple licensing is really necessary here, but I also don't see any problem with it.

@newpavlov Would you mind making another post, for completeness:

I license past and future contributions under the (Apache-2.0 WITH LLVM-exception) OR Apache-2.0 OR MIT licenses, allowing licensees to chose any of these at their option.

[newpavlov]

I license past and future contributions under the (Apache-2.0 WITH LLVM-exception) OR Apache-2.0 OR MIT licenses, allowing licensees to chose any of these at their option.

[brson]

FWIW I think Apache-2.0+LLVM exception or MIT is fine for this purpose. With the LLVM exception it's better-licensed than everything else in the runtime.

Adding the MIT license (as has been done) is required for compatibility with GPL 2.0 (this is why Rust is dual licensed). So everything in the Rust runtime must have a non-Apache, BSD/MIT-like license attached to it, with Apache as a bonus.

Personally I lean toward Apache-2.0/BSL-1.0/MIT trilecense over the LLVM exception, but there's definitely something to be said for just copying the LLVM license, since they have lawyers vetting it.

[brson]

Oh, I see that it's now trilicensed Apache-2.0/Apache-2.0+LLVM/MIT. I think that isn't necessary, Apache-2.0+LLVM/MIT would be fine, but the triliscense doesn't hurt, can trivially be trimmed to a dual-license later, and might have slight advantages, e.g. tooling might understand Apache-2.0 but not the LLVM exception.

[brson]

Oh actually, there might be a reason to prefer BSL-1.0 over Apache+LLVM - the GPL 2 compatibility. Now, I don't remember why Apache 2.0 is not GPL 2.0 compatible, so caveat, but the Apache+LLVM/MIT license presumably implies that "you are allowed to use the runtime exception, unless you are linking to GPL 2 code". Though perhaps the LLVM exception fixes the GPL 2 problem, or it has since been determined that Apache 2 and GPL 2 are compatible.

[tschneidereit]

Though perhaps the LLVM exception fixes the GPL 2 problem, or it has since been determined that Apache 2 and GPL 2 are compatible.

The LLVM exception is specifically meant to make Apache 2 GPL 2-compatible. The legal departments of at least two large vendors we talked to see this as valid and thus see just APL 2+LLVM as GPL 2-compatible.

[tschneidereit]

Ah, I now see that @sunfishcode made much better points regarding this over here.