The Wayland Protocol is simply a specification that is true. But there also has to be an actual implementation. The only implementation of Wayland Protocol at this point is the reference implementation that heavily uses Linux only system calls and is not practically portable to BSD or any other system. Therefor Compositors that use libwayland such as Weston and Gnome are also not portable. SystemD dependencies add another layer of incompatibility.<p>So yes Wayland Like X is in theory OS agnostic but in practical terms they are only as portable as there specific implementation.