What does it look like to use Schema for creating an original TTRPG? Appropriate crediting, of course, but what else?
On the last page, the "Unlicense":
You have permission to use any or all of the text in this document for your own purposes, commercial or otherwise, on the following conditions:
1. The document you re-use that text in includes a note stating "Some text is from Schema by Levi Kornelsen; used with permission."
2. Your document contains a link to a storefront or other distribution channel by which Schema is available (as of the time of release).
Additionally, you have permission to indicate compatibility with Schema where desired so long as you also indicate that Schema is by Levi Kornelsen.
...More straightforwardly, unless you're copying masses of text, just have at it; credit is nice.
If you want to copy text, put in the link and the "used with permission" above.
If you want to say "This is Compatible With Schema!", I'm hoping you'll put somewhere that I made Schema (but really, so long as nobody is going to think you're claiming you wrote Schema, that's actually enough). This is usually covered by the above, but like, if making a compatibility claim is the only bit, then that.
...
In addition, most of my stuff is available under these terms OR CC-BY 4.0, whichever is more convenient to you; the only reason this isn't is that I haven't updated the document recently, which... If you'd prefer a tested license over a direct permission, lemme know, and I can take a few minutes and do that.