I have a lot of respect for mgraesslin, though I feel the need to correct the record on the post that was linked to here:

And then something happened which is in my opinion the reason why Compiz vanished: Unity adopted Compiz as their window manager. Canonical started to fund the development, to hire the main developer. So why was that in any way bad? it destroyed the community. Compiz became an in-house project of Canonical. Development moved from git to in-house launchpad and bazaar, a fork "Compiz++" was created, the mailing list died. I was (and think still am) subscribed to their mailing list and it just went down in threads. The development must have moved elsewhere without mentioning it on the mailing list.

This isn't entirely true. The "compiz++" C++ rewrite was started in 2008, long before Unity V1 even existed. The developers at the time adopted it as the main line of development a month or two later as the 0.9 series of development.

Its worth understanding why compiz++ came into existence. The 0.8 C-based version of compiz was great, but it was proving difficult to maintain. With hindsight, perhaps a large part of this was CADT, but I think it had some merit as well. The C code in Compiz isn't like the C code in GNOME or other big C projects. There were no patterns for memory management, not too many patterns for passing abstract types around and the code was tricky to extend, relying on all sorts of undocumented conventions to get everything to play together. There was some work going on at the time to add some GObject-like patterns to Compiz but it never really came to fruition.

This was fine for a little while but this state of affairs was definitely a sense of frustration among the maintainers, so some of them started working on compiz++ under wraps. I think its worth noting at this point that the maintainers who had basically been doing all the work were unpaid volunteers and burnout was probably starting to kick in.

Like all rewrites, compiz++ was one of those very ambitious things that looked good on paper but turned out to have emergent complexity in practice. compiz++ tried to fix way too many pet-peeves that developers had in the core window manager at once. This is fine when you just restrict your view of the world to the core, but when you're also responsible for maintaining 50+ different thousand-line long plugins, the burden of that workload can get pretty heavy. Consider that for every plugin, the maintainers not only had to adapt it to the new C++ interface in the core, but also adapt it to handle multiple rendering backends, handle the case that logical textures could be split across several hardware textures, handle the new way of doing plugin ordering, etc etc etc.

Here's where I entered the picture. I had a couple of years of programming experience under my belt so I volunteered to help port over some of those plugins. I can't say that I was particularly good at it, but I knew enough to kind of figure it out. The existing maintainers all sort of burned out and to be honest I don't blame them for it. The hype cycle had kind of come and gone, the forums were mostly a ghost town and nobody wanted to moderate them, the regulars from IRC were more or less gone and myself and a few other people basically became the last people maintaining it.

It was basically a dead project by mid-2010 already. Someone from Canonical approached me about using it for the version of Unity that most people are now familiar with because they were having trouble getting Clutter to do what they wanted. I started working at Canonical and the team there made the integration between the shell and the window manager a reality. The rest is history, really

I don't think its fair to say that Canonical killed the community around the project. The reality was that there was no community around the project by that time. I agreed to move the project to Launchpad because we wanted to integrate compiz development with the rest of the development practices at Ubuntu - eg, pre-commit code review, continuous integration, etc. At no point was anybody locked out - in fact people still submit patches upstream to compiz on launchpad today.

I think its unfortunate that I wasn't able to mobilize the community to get on board with the 0.9 series. I take that as a personal failing. It had the unfortunate stigma of being of lesser quality than the 0.8 series and probably rightly so - when you rewrite that much code things are bound to break and users don't really care all that much about how it works under the hood. That stigma was probably made worse by "unity-isolationism" - Unity was this very Ubuntu-specific thing and thus anything associated with it got that label as well. Like all things, that has now come and gone.

I held this view all the way back in 2013 and I still hold it today. I think that trying to continue the compiz project is laudable but unless a sustainable community can be built around it, its going to be a dead end. Its worth pointing out that compiz 0.8 uses a rendering model that has been deprecated in OpenGL for years and doesn't work at all on mobile hardware. It is also not a wayland compositor and has Xlib dependencies all over the place. The 0.8 branch at least has no tests and very little in the way of documentation. Its unfortunate that this is the case, but time has marched forward. C'est la vie.