Installing Hard Wood Floor

I have a friend who took up their old floor (red oak), and with a little work I can make a nice dining room floor out of it. The problem is I live in a condo with gypcrete subfloors. This means that you can’t nail into it and you can’t glue down on it.

Has anyone encountered this? Any suggestions on how to do this? The only things I can think of are to pull up the gypcrete, which would be a huge pain and possibly legally require some new form of fire blocker, or to add a thick plywood base on top of it, which would raise the new floor height prohibitively high.

Am I missing anything? Is there a better way to do this? Has anyone tried this before?

Can you install it as a floating floor? If the are tongue and groove, you may be able to glue them to each other instead of nailing or gluing each one to the existing floor.