Not in forge, but as a mod.
cpw and Lex are currently implementing hooks into forge to make it more bukkit-like, as unfortunately the bukkit team have refused to cooperate with us.
So ya, it's possible.
In order to go smp, modloader mods had to use modloadermp in the old days. ML was client side only.
So yeah, ML mods don't work on dedicated servers unless they use MLMP/forge/hacks.