As unfortunate as it is, DrZhark has shown no signs of ever supporting SMP. It's possible that the eventual addition of a modding API to the game in future updates will make this possible, or that Notch will include Mo' Creatures in the vanilla game (here's hoping, huh).
There is already a SMP mod for mo creatures. Sadly, it doesnt work with bukkit yet. http://www.minecraftforum.net/viewtopic.php?f=1023&t=222855
I think the main reason that mods like mo creatures haven't gotten much traction with the bukkit crowd is that as soon as you mod a server in a way that requires a client mod as well, people with unmodded clients start crashing when they connect to your server. It's also very likely that mo creatures spends most of its time modifying areas of minecraft that aren't exposed by bukkit yet.
Yeah Lodran I love your plugin. I think the modder that is porting mo creatures from ssp to smp is eventually gunna port to bukkit, but it'd prolly be better if a bukkit modder did it instead.