Is this something that could be used in Sketch? Or just Photoshop?
I can't tell from that website whether these brush files are .tpl files. If they are, you should also be able to use them in Sketch. Here's a quick tutorial about bringing .tpl brushes into Sketch: Loading .tpl files into Adobe Sketch – AJ Aiken It actually refers to importing Kyle Webster's Photoshop brushes, but it explains how to bring them into the app in a pretty thorough way.
One thing to keep in mind; not even all of Kyle's brushes are compatible with Sketch (that is, when they're brought into the app, they're greyed out). It might not be a bad idea to ask the creator of these brushes to do some testing with Sketch to see if they can be brought into the app (she'll be able to test them without paying for them first).
Hope that helps a bit.