No, GL4 80/90 is not fine! Only the recommended Qtrac TCL-1 lube should be used on a Qtrac unless it has been converted to part-time drive via MileMarker conversion kit.
The Qtrac has brake cones and clutch plates inside it that require a certain level of lubricity to provide the differential action necessary for full time 4WD. Without the right fluid these parts will wear prematurely and once they are shot the tcase is essentially shot and forward motion will cease to exist unless you engage the emergency drive.
Look here for detailed info on the BW-1339 Qtrac tcase: http://jubileejeeps.org/quadratrac/index.htm
edit:rishar you need to quit telling everyone that GL4 is the recommended oil for tcases. It isn't recommended for every tcase or necessary unless the tcase and transmission share fluids.