The trademark for Beast Hunters may very well have expired considering, if it was ever filed at all. Even if they had filed it, TFPBH came out in 2013, and let's assume that the trademark was filed in 2012, that's still a good thirteen year gap. Surely any trademark would've expired by then. We didn't see Hasbro using the Beast Hunters name at any time between 1999-2013 so there doesn't appear to be any sign of them maintaining the trademark through usage. I suspect that the homage was done more out of opportunity.