depends, if your server is basic you'll need modloader for mp and other plug ins installed in the minecraft server jar (others should be metioned with the mod, and you will also need the mod in singleplayer installed, that should work, for bukkit it should be the same procceses for some for installing mmods in the jar and adding plug ins.
Chat with our AI personalities
Check out the link below for a guide of how to install mods in Minecraft.
minecrafts popular servers are pixelmon mods
Depends on your server host.
Yup.
If you are looking for a easy way to install mods, someone made another Minecraft that can be used for downloading mods easier.