Dear Serge,
I am very happy to hear that you want to take over the project.
Personally, I am currently not able to spend any time on GEF. Therefore, I really need to step down from my role as project lead. On top of that, I am not aware of any real development on the GEF project for the last two years (approximately). Hence, the project is desperate for some love, and everyone who was involved up to now would probably be very happy to see people giving that.
I strongly believe that transitioning to JavaFX was a good idea for GEF. However, of course I know that a lot of software depends on the legacy API. Additionally, many modern developments consider web technology over something like RCP, so JavaFX GEF definitely is a niche.
Anyway, it might be time to reconsider where to take the GEF project in the future. In one of my previous projects a long time ago, I made the mistake of not handing it over to an interested party who had the time and eagerness to push it further. As I hope to have learned from that mistake, I am more than happy to help you take over GEF or just GEF Legacy.
In order to do this correctly, it is important to align with Alexander and his idea for the future of the GEF project. I hope that he will answer this email, too.
I am not sure if GEF Legacy could be transitioned into a separate Eclipse Project that you could maintain. It would make sense to ask PMO/EMO for support, I assume. (But I want to wait for Alexander to join the discussion before approaching them.)
AFAIK, the proper way to get you involved with GEF and fully take over the project, would be following the processes as explained in the Project Handbook [1]. Since you already prepared a lot of contributions, I could see you bring them into the GEF Legacy codebase via Pull Requests one by one, building up trust with the team, and justifying a committer election. As soon as you are aligned with Alexander w.r.t. the future of GEF, I would welcome it if you could replace me as Project Lead. I can imagine you maintaining GEF Legacy, while Alexander focuses on JavaFX GEF. However, there are a lot of options, and it really depends on Alexander's vision for the future.
Best regards,
Matthias