Starting in early July, the whole Tor/Forge e-book catalog will be free of Digital Rights Management (DRM) — which means you'll have an easier time copying them from one device to another. And it also means that Tor's books will be available from e-book retailers who only stock DRM-free books.
In a press release, Tor Publisher Tom Doherty was quoted as saying:
Our authors and readers have been asking for this for a long time. They're a technically sophisticated bunch, and DRM is a constant annoyance to them. It prevents them from using legitimately-purchased e-books in perfectly legal ways, like moving them from one kind of e-reader to another.