I appreciate you coming forward to ask more about the license! It is, indeed, CC-BY. I actually should write my own license for these since the only no-no for me is people re-selling these assets and/or claiming these are of their own making. But yeah, add the credit anywhere you find it plausible/feasible - no nitpicking there - and we are gold, redistribute it with your tool to your heart’s content!
I really like that you have a very solid plan set and I am more than happy to be able to contribute to it in such a small manner. If you need more complex proof of concepts I will gladly hand you a key for each full tileset I have now and a couple more there are to come - but, for these, I would ask to not redistribute the full version, of course.
Let me know your thoughts!
Oh yeah, also let me know if you find any weirdness on the fonts. I am still a newbie when talking about fonts and I know that some improvements can be made, especially regarding the kerning pairs.