[crazypython]

> The use of GPL'd files means that the gem itself has to be released under the GPL. Since the gem is now under the GPL, dependencies are also under the GPL.

No, that's not true. You can dual-license dependent software under GPL and MIT. The GPL merely requires a license at least as permissive as it.

[Denvercoder9]

> The GPL merely requires a license at least as permissive as it.

No, it requires a license that's at least as permissive as it AND that imposes the same obligations (i.e. source distribution, etc.) on the licensee.

Dual-licensing dependent software under the GPL and MIT only ensures that you can rip out the GPL dependency, and then use the (formerly) dependent software under MIT. The whole package is still GPL and imposes the same obligations on derivatives of the package.

[crazypython]

Yes, that's what I'm saying.

[eek04_]

You can dual-license if you own the full copyright ownership but if you include GPLed stuff (and don't have the full copyright ownership) you'll have to GPL the result.

As for "at least as permissive" - it requires no further restrictions, but it adds a bunch of restrictions itself. And there's no other license that doesn't add restrictions - MIT adds restrictions to reproduce the MIT license, which is an extra restriction. The restrictions are attempted excused by the FSF under the "attribution" clause of the GPL, but it is not clear to me that is valid and it has not tested by any court.

[crazypython]

I am fairly sure MIT's license is considered an "appropriate legal notice."