All of it. Every track you download from Digital DJ Pool is a standard MP3, so it works with any DJ software — Serato, Rekordbox, Traktor, djay, VirtualDJ, you name it.
Download a track (or a whole crate), then drag and drop the file straight into your software's library. That's it — no conversion, no special format.
The tracks are yours to keep forever, even after you cancel, so your software library doesn't go anywhere.