I believe context is important, so here is a little story.
Let's imagine (all characters and events in this story - even those based on real people - are entirely fictional) that Alice has developed a software, 'Sierra' - starting from a preexisting educational code - during her PhD, and has subsequently used it and developed it during her academic career. 'Sierra' is software for base scientific research with little or no purpose outside academia, and many people who worked with Alice over the years have contributed to it in some way. The code was never made public.
Unfortunately, Alice dies prematurely, and the last 3 people working with her - Beth, Charlie, Dave - decide that the best way forward is to release the whole thing as open source. Other previous collaborators and contributors agree, and they get the permission from the author of the educational software which 'Sierra' was based upon (the closest person to an owner of the code after Alice) who agrees , but does not want to be further involved.
Dave, who is still employed on the last active project of Alice, sets about to tidy, debug and test the code, so that it is in a state where it can be made public. For reasons not entirely clear, things go south: Dave rebuffs all offers of help and suggestions from Beth and Charlie and eventually releases 'Sierra' under
EUPL license. Because of Dave's unwillingness to collaborate, Beth and Charlie decide to fork the project.
The question is: can Beth and Charlie change the license of their fork from
EUPL to, for example,
GPL2? The reasons are:
EUPLis designed with compatibility with EU law in mind and, while this is not a problem per se, it is also not relevant for scientific software which is not tied to the EU and is by design international in scope and objectives.
Dave has chosen the license without consulting with any of the other previous contributors. It is true that he has done a lot of work on the code, but surely that doesn't transfer ownership to him, enabling him to take this decision by himself. In addition, the choice of the license seems to be at least in part motivated by political reasons, which is inappropriate.
'Sierra' works with a customized version of another software which is under
GPL2. The two licenses are compatible, but it simply makes sense to distribute both programs with the same license.
This is not just a question of relicensing, and whether one licence allows conversion to the other. Even if that is not the case, there is also the question of whether the original choice was in fact legitimate (hence the story above) and therefore whether the change can be done regardless.
Dave was in charge of preparing the official release and he did major updates and changes to the code, so he has some IP claim. However, there were several other contributors (besides Alice) before him, and it was implied that the release of 'Sierra' would be made in agreement with Beth and Charlie.
The author of the original educational code approved the
EUPL (he was the only person consulted by Dave), but since he is not interested in being involved, he would likely be fine with whatever is decided by Dave, Beth and Charlie. Given the purely scientific nature of the software, the legal heirs of Alice are very unlikely to have an opinion.
I think it boils down to two options:
Dave had the right to unilaterally pick a license (with the only approval of the author of the original educational code). If so can the license of the forked project be changed from
Dave did not have the right to choose a license without consulting other former contributors. In which case, can Beth and Charlie do whatever they want with their fork?