If I were to want to experiment with my own gym app idea, would I be able to license the data set?

Are you speaking about videos ? If yes, it comes from a partnership, and while it's allowed for use within this open-source project, it’s not automatically "sublicensable" let's say.

That said, if you’re interested, you can either:

Reach out directly to the partner for permission, or

Let me know more about your project idea, and I'd be happy to introduce you or ask on your behalf to see what's possible.