That kind of thinking is one of the biggest problem with Wikipedia at the moment. Sourcing should always come *before* writing. The source is where the information came from, that's what "source" means, so you have to have the source before you can write the article. Adding sources afterwards is a way of fixing a problem - unsourced articles - it should not be a part of the standard process of writing articles. The problem should never be created in the first place.

I'm not sure what you mean by "sourcing these notes" - can you rephrase that?

Oh certainly, you don't need to add the sources to the code as you go along, but you need to know what the sources are. The sources should be added in the same editing session as the article is written, the exact order within that session is up to the writer. Someone else coming along after you've written the article and trying to find sources for your statements is completely wrong - it's not what "source" means. They are effectively rewriting the article. If you want different people to do the sourcing and the writing, then the sourcer should find the information and add it as bullet points to the article, with correct references, and then the writer comes along and makes it read eloquently. The other way round is completely wrong.

When I say editing session I don't mean the time between clicking "Edit this page" and clicking "Save", I mean the time between sitting down at the computer and standing up again. If someone wants to save the page multiple times to avoid losing all their work if something goes wrong, that's fine, and they can put the references in at the end. I think it's easier to do it as you go along, but it's a personal thing. If they stand up and walk away from the computer for the night without adding the references, then they've just put an unsourced article on Wikipedia, and that's a bad thing. It's not necessarily worse than no article at all (some would say it is), but it's still a bad thing and shouldn't happen. When you write an article, you should automatically know what the sources are, because they are where you got the info. If you've written the article without finding sources, then it's written from your memory, which is not reliable and the entire article should probably be deleted. Adding sources is really easy, because you've already done the work before you started writing the article, so there is really no excuse not to add them.

In most cases, probably the university. They generally claim copyright on everything anyone does within 100 miles of the uni. I don't think it matters though - the mathematics isn't copyrightable, just the way it's written in the notes, and I don't think anyone is planning on just typing up the notes, they're talking about using them as sources for an article.