If you want legal stems for EDM music. Beatport throws you a bone every now and then. They have monthly remix competitions where they have an artist release the stems for one of their tracks on beatport. Artists that have done this is Bingo Players, Zedd (who actually got signed by winning a beatport contest), Skrillex, Above & Beyond, Cedric Gervais,John Dahlbäck.

Here's another documentary about compyrights. Btw both of the makers of these videos, highly encourage their audience to sample, remix, spoof, remake their videos.

Here's a really good documentary about copyright laws. If you're into sampling, you NEED to watch this. "Immerse yourself in the energetic, innovative and potentially illegal world of mash-up media with RiP: A Remix Manifesto. Let web activist Brett Gaylor and musician Greg Gillis, better known as Girl Talk, serve as your digital tour guides on a probing investigation into how culture builds upon culture in the information age. Biomedical engineer turned live-performance sensation Girl Talk, has received immense commercial and critical success for his mind-blowing sample-based music. Utilizing technical expertise and a ferocious creative streak, Girl Talk repositions popular music to create a wild and edgy dialogue between artists from all genres and eras. But are his practices legal? Do his methods of frenetic appropriation embrace collaboration in its purest sense? Or are they infractions of creative integrity and violations of copyright? This documentary is released under Creative Commons Attribution - Noncommercial 3.0 Unported license."