XDMCP without xdm?

[Stuart Ballard <stuart@wuffies.net>]

Is there any way I can allow remote hosts to access my machine via xdmcp
without running xdm on the machine itself? (running xdm seems to lock
the machine completely on a regular basis). Would running xdm without
managing any local displays solve the locking-up problem? Alternatively,
does anyone have any experience with whether any of the other display
managers (kdm, wdm, gdm, login.app, ...) solve the problem of locking
machines up? Do those provide xdmcp?

Failing all this, is there a way to get a similar effect using startx?
(ie, start an x session but run all programs from another machine).

TIA,
Stuart.