Amazon and BN sell _some_ books without DRM as well. To encompass your Sanderson example, all of Tor ebooks[0] are DRM free regardless of distribution channel.
Oh interesting, I guess I haven't paid much attention to the ebook markets since I bought my Nook Simple Touch, I've just made a habit of checking Kobo first because they were the ones offering no-DRM at the time. Good to know!