Of course you have my permission! I license most of my work under a CC BY-SA 4.0 license, which generally means you're allowed to copy it, redistribute it, modify it, and make transformative content for it both commercially and non-commerically, as long as you mention me as the original creator and distribute your transformative content under the same license.
Also it feels super flattering that someone wants to write adventures for this!
The fonts I used were Seagram tfb for the titles and Source Sans for the rest of the text.