I was just wondering, since forge now comes in Universal package, would that mean any mod's made in MCP with forge also work on the minecraft_server.jar? It's confusing cause I thought the class names on the server jar was different.

The names are no longer different, so as long as the mod is coded correctly it can be installed on the client and server.

Yup, if a modder isn't stupid and does his mod correctly. Then the same exact code will work on the client and server, which means that he can bundle both in one.

Case an point Forge, we edit a bunch of base classes, yet we're still able to make a universal distro.

There is no valid reason a modder shouldn't be able to.

And if he doesn't hes just making more work for himself

Just another question: I was looking at CPW Iron Chest mod source, and noticed that he placed CommonProxy as his serverSide proxy. Does that mean that the CommonProxy could be called on the Client as well?

If you notice, his client proxy extends CommonProxy.

I saw that, so it does get called. Okay cool.

The client has to extend the other, or the field has to be a shared supertype such as an interface. The sided proxy pretty much enforces this. The practice that has developed, and its a good one is to have the server as a "super" and client as a "sub"..