Combining PolyForm licenses is certainly possible for many projects. For example, at least in my mind, Noncommercial and Free Trial kind of want to work togethe

Combining PolyForm licenses is certainly possible for many projects. For example, at least in my mind, Noncommercial and Free Trial kind of want to work together, for a pretty common use case. Folks involved in drafting certainly thought about multi-licensing. That said, neither I nor PolyForm Project have fully vetted all combinations. The easy "out" is "talk to a lawyer", to make sure you avoid any footguns. But I not so secretly hope the licenses are easy enough to read, without legal help, for diligent folks to work through implications themselves.