I was under the impression that they treat a VM like a separate machine - but now I'm not sure. I started IDEA in OSX and a Windows 10 VM on the same machine ten minutes ago, and so far neither instance has complained. I know IDEA has complained when I've run it on the Mac and my ThinkPad.

If this is legit and I can run IDEA on the host machine and in one or more VMs on the same machine, that would be a very good thing for multiplatform developers.