This post will be short and quick, but also for fielding questions. In short, you can use these brushes to create maps and sell those maps or put those maps into products that you then sell. You cannot sell the brushes themselves, or the images that make up each individual brush. 

You get permission to make stuff to sell using these brushes by buying this map pack. The licence does not expire. If you get the brushes from a friend without buying them, you can't charge money for what you make using them because you as an individual have not paid for a license.

Anyways, I will expand on this when I am less tired (and if I get any questions).