As always, wonder what a particular "free" thing is selling and to whom. In this case it's something called BHEX, to NASA.

As Project Scientist for BHEX, I am of course excited about the project and eager to spread the word about it! But as I wrote in my other comment, what this is really trying to "sell" is gravitational physics to students interested in black holes, and this effort is supported in part by the National Science Foundation.