KDE's DCOP, the D-Bus predecessor, worked over network due to using some X11 client-to-client communication mechanism.
Of course this isn't an option for something that also needs to be able to provide the equivalent to the D-Bus system bus.
D-Bus, however, could make use of other techniques, e.g. certificate based authentication over TCP, etc. but on the other hand that would limit the feature set available to clients which wanted to support that (might be OK for the majority of clients though).
Kroah-Hartman: AF_BUS, D-Bus, and the Linux kernel
Posted Feb 10, 2013 19:36 UTC (Sun) by hp (subscriber, #5220)
[Link]
there is no conceptual problem tunneling dbus over X or adding a secure TCP auth mechanism. it already works if you have a network home dir in common (because the "cookie in homedir" auth then works).
it's just a matter of someone caring enough to do the work. in around a decade not a single person has wanted this enough to code it or pay to code it. That's why it didn't get coded.