A little over six months after first being announced (last100 coverage), LimWire’s DRM-free music download store has finally opened for business.

The U.S.-only store currently has a catalog of 500,000 tracks, with thousands more to be added “daily”. All music is offered as MP3s encoded at 256 kbps and priced a la carte at 99c per track. Additionally, LimeWire is offering pre-paid plans similar to eMusic, ranging from $9.99 per-month for 25 downloads (40c per track) to $19.99 per-month for 75 downloads (27c per track).

Despite being at least six months in the making, the LimeWire music store is a purely Web-based affair and doesn’t yet tie into the LimeWire P2P client. On that note, LimeWire says that in the future it “will be releasing a version of our file-sharing software optimized for integration with the Music Store.” That way, LimeWire can begin to leverage its, albeit shady, brand recognition amongst music down-loaders in an attempt – like Napster before it – to develop a legitimate business in the onlooking eyes of the music industry.

All in all, Limewire is entering an increasingly crowded market with very little distinction beyond its name and pre-paid pricing, that includes big hitters Apple, Amazon and eMusic, as well as other recent DRM-free converts such as Wal-Mart — see our Digital music: 2007 year in review.