So, we should note that "Using 5.1cc" doesn't mean "5e compatible". IIRC, Mutants and Masterminds used the 3e OGL, but you wouldn't call it compatible with D&D in any meaningful way. And that image does not say anything like "compatible with the world's most popular RPG" or the like, so I assumed it was a stand-along game, not a supplement for 5e.
Ultimately, what license they use isn't material. What game they are supposed to work with is.
And, I have no control over what tags exist. That's an admin thing, not a mod thing.