Curiously, the inclusion of ThunderHumor theme in GMEdit is entirely coincidental - I had it added to local themes directory for testing at one point, and the build script packs updated files into a ZIP without removing the old ones, so it made it in and stayed there without me ever taking notice.
If you've seen their streams, they do have a matching theme for GMS1, but it's based on some other theme, so I'm not sure if they would be able to release it or not.