So a friend of my got a whole bunch of reclaimed Acacia and he wants to put it in his condo which he later learned has a Gyp-crete subfloor.
Putting down a few layers of plywood is out of the question as it will raise his floor too high, I recommended pouring self level and gluing it down. Is this the best way to go? Or is gluing down directly on the Gyp-Crete just as good an option?

I did a glue down over sanded mortar which was a radiant heat job. The more common material to use in his application was actually gypcrete but he chose to use sanded mortar as it costs less. I used Sika bond T-55 and the flooring stuck as solid as could be. TO my knowledge , gypcrete , once dry and cured will hold flooring adhesive.

The bigger issue is moisture transference. The slab needs to be tested for moisture content and sealed if it is too wet or tends to get wet.

Sounds like a crap shoot to me. Do you know whose self leveler says it can go over top of gypcrete and how to prep it accordingly?

Just because you find a solid floor cheap, don't mean you should do it. I have other jobs that are less risky to do and will make me money and not risk my license, money and time.