> I thought the usual solution when we disagree irreconcilably with a maintainer was to fork and rename?Yes. But that requires someone, or a group, to take responsibility for that and support the fork. Maintaining a filesystem can be a complex undertaking.
> Seems like everyone quit Hans and nobody rallied the project back together.
I think it was more like he was the core of the project with others contributing. Once he was out of the picture no one else had sufficient passion and/or time for it to take on the mantle of project lead sufficiently (to push Reiser4 onward and eventually getting it merged into the mainline Kernel and maintaining Reiser3 in the meantime & further forward).
While Reiser4 is still maintained, it has never been merged into the mainline kernel limiting its support in common Linux distributions. I don't know if that is because the current maintainers have tried to have it merged and failed for some reason, or if they have not pushed of its inclusion at all.
What is deprecated and due to be removed is Reiser3, which is not actively maintained. There are some technical issues that would need addressing soon if it were to remain, and in any case an unmaintained filesystem is a dangerous thing to rely upon if you can avoid doing so. It isn't being removed because of who started it, it is being removed because it is not well enough supported for mainstream safety.
Reiser3 won't be removed until some time in 2025, and unless you need the latest latest kernel at all times an active setup will keep working for a while after that (until the older kernel it uses falls into EOL), so you have plenty of time to migrate if you need to.
If a lot of people were relying on Reiser3 there would be a lot more noise about this. People using Reiser4 are building their own modules (or patching a kernel tree and building it in) already and this will not affect them.