Qtrax, the ad-supported music download service, announced yesterday that it had completed licensing deals with all four major music companies, with Warner Music Group the last to come on board.  It intends to relaunch its service next month.

This is a remarkable bounceback from Qtrax’s beginnings as an unauthorized, Gnutella-based file sharing service and its previous premature launch announcement without certain major-label licensing deals.

Qtrax is a free music download service.  It uses Windows Media DRM 11 to count music plays and report them to a server that computes royalty payments; it also uses the DRM to ensure that users watch ads targeted to their music listening habits at least once every 30 days.   Qtrax intends to make a profit from ad revenue.

Music will play on PCs and can be transferred to certain portable devices; it remains to be seen whether Qtrax has figured out a way to enable approved transfer to devices other than those that support Windows Media DRM.  It will also be interesting to see how big a concern Qtrax’s playcount reporting will be.