”Come and relax now,” beckons Dave Matthews as you enter his band’s site. But what’s this? A ”security scan”? Seems a tad Orwellian for such laid-back musicians. Once you’re in, though, behold the goodies: QuickTime video, Liquid Audio clips, sheet music, and, naturally, a chance to buy DMB’s newest live album, ”Listener Supported” — no background check required.