Spout plans to create a client side plugin system, which will unlock the ability to add custom blocks, monsters, and items to the game. Imagine joining one server, and having it automagically download all the new game content and install it seamlessly. Then, log out and join the next server, totally vanilla, without ever closing the game.
Cool, sounds like they're trying to do exactly what I want, will help a lot with the mods. Can't wait for them to finish. (Current versions of spout seem to just add a few minor features, they don't have any of that advanced stuff yet).
Our business in life is not to succeed but to continue to fail in high spirits. -- Robert Louis Stevenson