I’m working on a "for fun" project in my spare time. I may end up making it Open Source and this makes me wonder what I need to think about if someone cares enough to contribute to it.

• Do I need to have some sort of legal mumbo jumbo about “if you give me yer code, it accepts the same license as the project, bla bla bla” (what is the norm here?)
• Is there a way to check contributed code to make sure it is not plagiarized or would that liability fall on the contributer?
• Are there any other gotchas, standard/common practices I should follow, recommendations, things I need to think about?