davidj919account.mojang.com/documents/minecraft_eula

ONE MAJOR RULE

The one major rule is that you must not distribute anything we‘ve made. By “distribute anything we‘ve made” what we mean is “give copies of the game away, make commercial use of, try to make money from, or let other people get access to our game and its parts in a way that is unfair or unreasonable”. So the one major rule is that (unless we specifically agree it – such as in brand and asset usage guidelines) you must not:

give copies of our Game to anyone else;
make commercial use of anything we‘ve made;
try to make money from anything we‘ve made; or
let other people get access to anything we‘ve made in a way that is unfair or unreasonable.
…and so that we are crystal clear, what we have made includes, but is not limited to, the client or the server software for our Game. It also includes modified versions of a Game, part of it or anything else we‘ve made.

Otherwise we are quite relaxed about what you do - in fact we really encourage you to do cool stuff - but just don‘t do those things that we say you can‘t.