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I have forked a project that was released under the GPL and made substantial modifications, however there are still some parts and general ideas that are the same as upstream.
Due to user interest I am wondering how, if at all, I can relicense the project. Another developer and I have attempted to reach the upstream dev multiple times but he has never responded. Since there hasn't been updates in several years I'm considering the upstream project abandoned and looking at other options.
GNU lists Apache and Modified BSD as GPL compatible, which are 2 licenses that come up often and are less "viral" than the GPL. Since they are compatible can I Just relicense my project with either of those licenses?
If I am unable to do that, are there any options I have to change the license? It's important because there are several users who have software that is incompatible with the GPL, and therefore makes it impossible for them to adopt the project. I'm trying to avoid simply rewriting everything, which is hard since there's only a handful of good (or correct) ways to accomplish the project goals and I'd end up splitting hairs on what constitutes "derivative" code.