A New York judge gave the rapper the green light to travel, with a drug counselor, to perform a concert Friday night -- then it's back to the rehab facility on Saturday. He was also allowed to host a Thursday night gig in NYC.

X's attorney, Murray Richman, tells us ... he's always required to travel to his shows with a rehab counselor and gets drug tested while he's on tour. We're told he's been granted release about 10 times during his rehab program and hasn't failed a test.

Richman says DMX covers all of the counselor's food and expenses while they're traveling together.

When we last saw DMX, it looked like rehab was doing his body good.