When we moved into our villa in Doha, no one asked for a marriage cert, so it is possible. In fact my neighbours are two guys living together. They are straight, but decided to cut costs and move into the smae villa. if you get through imigration seperately just buy yourselves a cheap wedding ring and no one will be any wiser.

as most people on this thread have advised, it is frownded upon here but you can get away with it.