Ask HN: Free psychological tests, that don't need to be licensed

I'm trying to put together a resource with all the free (as in beer), copyright-free, psychological tests that I can get my hands on. Tests that don't need to be licensed, nor need permission to be available on this resource I'm building.

People will be able to come and do tests as they please, and discover how they score on any of these tests. (This is not a unique idea. There are plenty other sites that exist along similar lines.)

My question for you: if you have experience with this sort of thing, how did you go about figuring out which tests could be used without permission / license? (Due to past bad-experiences with negotiations related to such things, I don't want to bother with tests that need permission / license.).

Thanks in advance.