What about SymbOS for new enhanced ZX spectrum Z80 8bit machines as ZX Next ?? (enought ram and colours)
Right memory paging for SymbOS????
More user for our favorite OS 
Noop !!! PCW/Joyce too, myfriend 
Beside the very big problem, that SymbOS is multiplatform, and from my (already very big!) experience that people don't care so much about any other system which is not their own one, when developing things...
I wonder if there has every been a BIG successful open source project for an 8bit system, which lasts for years? 
(speaking about a bigger project)
I am still open for making SymbOS open source, my most concern is what Edo said, and I don't have a fulltime job like Linus for controlling github commits. Anyway I think the day is coming, when I will open all this (like anything else of my 8bit stuff).
I don't see much big compatibility issues. More precisely, there is a problem, of course. But, the software itself can control the software for launchability on different platforms by asking the system for a host ID. Further solution - either the program works or exits with an error message.
It's like with Android. Some software works on your ABC China, and some does not.
Meanwhile, the Sprinter community is growing. New boards are being produced. Currently in development for ATX and ITX boards. Already created a network card (based on ESP-12F). It would be desirable source codes Symbos. I'm not asking the author to port it to this machine for me, we can handle it ourselves
SymbOS being closed source is pretty much the only reason why I never really bothered to dig deeper into it and see what it is/has/does (plus I own only ZX Next HW).
I wouldn't worry about forks too much, most of the users will first follow and try the "official" SymbOS, so as long as the main project is actively maintained and working (and listening to user needs and accepting meaningful pull request), it will keep easily major "share" of users, and any forked incompatible version will be relevant mostly only to author and to users which has the same issue which the fork does resolve.
Only if the main project would become very inactive and some fork would be consistent in updates and maintenance, then I guess over 5-10 years people would maybe start to consider the fork the "main" SymbOS.
In my experience it's difficult enough to promote even free and free (price and rights) software, and to get some meaningful contributions and new contributors, any small hurdle can filter out the remaining individuals who had some early interest (unless you are some large popular FOSS project like linux/gimp/... which can afford to filter contributors more), so being worried about incompatible forks is IMO premature, if you would open SymbOS, it's very likely for several years nothing would happen and almost nobody would seriously contribute any way. 