The celestial jukebox is back, far too late to matter. Napster is now selling a library of 6 million songs, from all four major labels, as MP3 files, a format which lacks copy protection and hence is compatible with any number of devices — most importantly, the iPod. In other words, the state of affairs that existed nine years ago at Napster's original launch, save for the 99-cent fee now charged per download. Egghead Netscape cofounder Marc Andreessen notes the irony without explanation. For the slightly less brilliant among us, here it is: The record labels, having killed Napster once, have now rallied behind it, hoping to weaken Apple, a company whose iTunes store is already the dominant music retailer in the U.S.