The popular libraries for writing Wayland compositors consider Linux first, and BSD support is bolted on later.

BSD devs can fork/write libraries too if they choose to or decide to not implement wayland which is valid too.

I din't see anyone complaining that xorg or xlibre is providing source that build and work for haiku, redox for example. My understanding is that both projects have to maintain their own patchsets to make it work.