You can use Pidgin, set up to use MSN account and it will work.Tested at least for messages.But actually MSN is pretty sucking protocol with brain-damaged design.It has nice features like custom smiles, avatars and other extras.But this is worth of nothing when protocol may fail to deliver message from Alice to Bob without letting Alice know delivery has failed so she thinks Bob just ignores her messages.There is really better alternatives in the world.MSN is only popular just because nasty MSN client is built in into Windows by default (and even pretty hard to remove even if you don't like it) and people are not aware of better ones.That's how abuse of monopoly works :\