There's a body of practice in tabletops that I have long wanted to become a scene. I also think it would benefit a fair number of people (including me, of course) if it were such a scene. So let me speak it into being:

It's called New-School Kitbashing.

New-School roughly as in, finding its mechanical antecedents in games after D&D 3rd edition (setting it apart from Old School) and/or in games influenced by Story Games and the Forge (and its Diaspora), that being a common "New School" era.

Kitbashing as in producing rules by or for mashing up such New School stuff, and with an eye to ongoing efforts at same (which doesn't necessarily entail an open license, but we're definitely talking permissive-of-borrowing stuff).

The folks in this scene talk about stuff like, say:

Cool stuff they or others have made that's intended for mashup; procedural bits of kit and system-agnostic whatsits. The results of their mashups, and the sources; "I made these rules here with stuff from A, B, and C". Games they kicked over and found great parts in. And, obviously, what they're playing and how they're using all this stuff.

I'd be excited to hear about all of that. I strongly suspect others would be, too.