It’s official… Sony (NYSE: SNE) BMG will begin selling DRM-free tracks through Amazon‘s music store by the end of the month, confirming reports that surfaced last week. In the announcement, Amazon (NSDQ: AMZN) touts the fact that it’s the first download store to offer DRM-free tracks from all four major labels—a jab at Apple’s (NSDQ: AAPL) iTunes, which isn’t mentioned by name. Sony BMG’s decision follows a similar move from Warner Music and it represents a pretty significant win for the DRM-free side, given that just two years ago, Sony BMG was caught up in the disastrous rootkit fiasco, in an attempt to prevent CD copying. Though not as headline grabbing, Amazon has clearly been winning over independents as well. The latest release claims 33,000 indies now sell through the site, up from 12,000 when it first announced plans for the site. More in the release.