Schema is in the beta stage of a new iteration - think of this as an edition change, complete with draft, alpha, beta, and release stages. The changes are compiled from fully tested material - it's only the document that needs polishing up to spec. Comments are active for this document, and if you've got any to give, I'm very interested!
Schema is a light engine for tabletop roleplaying with complex stakes.
Breaking that down - It is an engine, rather than a game, because assembly is required - you'll need to provide a setting and do a bit of configuring before it's ready to go. It's an engine with complex stakes - the kind of thing you might see in a Powered by the Apocalypse game, but built on the fly with a "stakes sheet" in the center of the table.