"generalized weston-launch" / "logind without the d"
A setuid launcher / wrapper that passes GPU/vt/input file descriptors to an unprivileged display manager (typically, a Wayland compositor) and controls the virtual terminal / DRM master. Also provides shutdown/reboot/suspend commands like logind does. But does not support any multiseat stuff.
Currently supports FreeBSD only, but can be ported to Linux.