> You don’t have to distribute the plugin as xGPL but you do need to make it compliant.
My reading of the GPL is that if you are the rights holder of some software, and there is a xGPL licensed plugin to said software, you can only distribute changes to the plugin if you also distribute your software as xGPL. In other words it is impractical for you to make changes to xGPL licensed plugins to your software.
> Many companies will instead do shim/bridges that aren’t GPL themselves but something like MIT. The bridge talks to proprietary code and the GPL but doesn’t bridge the license over as a result.
Unless the GPL was enshrined in some law I'm not aware of, it's likely to be a a breach of contract, not necessarily "illegal". If a court rules against you, in most cases the worst that can happen is having to pay some redress to the developer and stopping what you were doing.
> Unless the GPL was enshrined in some law I'm not aware of, it's likely to be a a breach of contract, not necessarily "illegal".
The GPL licenses give you specific permission regarding copyrighted work, provided you comply with the terms. If you do not comply with the terms, you do not get the permissions. If you then do something like distribute the work you are not in breach of contract, as you had no contract to breach. You are in breach of copyright, which is not legal as there are laws prohibiting copyright infirngement.
> If a court rules against you, in most cases the worst that can happen is having to pay some redress to the developer and stopping what you were doing.
Why do you want to leave this possibility open? Why not just avoid GPL and use a licence which is clearer, where you don't have to first go through litigation to understand the terms of the licence?
To be supremely pernickety one might argue that copyright is a tort, so it is tortuous infringement, which is unlawful (not allowed by laws) but not illegal (criminal).
But then one might also argue about how many copies of the GPL fit on the head of a pin.
However, in some jurisdictions some copyright infringing acts are deemed criminal; so not only is such argument futile but it can also be wrong according to the facts of the case.*
My reading of the GPL is that if you are the rights holder of some software, and there is a xGPL licensed plugin to said software, you can only distribute changes to the plugin if you also distribute your software as xGPL. In other words it is impractical for you to make changes to xGPL licensed plugins to your software.
> Many companies will instead do shim/bridges that aren’t GPL themselves but something like MIT. The bridge talks to proprietary code and the GPL but doesn’t bridge the license over as a result.
I'm fairly sure this is not legal, see https://www.gnu.org/licenses/gpl-faq.en.html#GPLWrapper
The point is there is too much in the GPL that is open ended and can only be known for sure after litigation.