>>120
I've never seen akku or snow have edwin extensions and I'm assuming something must exist even if it's a dead project from decades ago. Usual code hosts come up with about 4 edwin extensions when using the equivalent ?lang=scheme&q=edwin and they don't have a sexpr entry.
I also don't like the way akku handles srfis but other then that it's a better source once you understand (chibi) ~= r7rs. Which is worded horribly and I'm sure a (chibi package) will eventually use a chibism.