I don't think there is! but Exodus has a .txt "demo" available if you want to read how it works with the structure, and Before the Spire Falls is pwyw (but you should pay something for it!). The thing is, it's such a simple and elegant framework that I can't really think about what an SRD would look like? like, there's not enough.. mechanic to make an SRD for. The basic thing is super simple: you gain a token if you make a weak move and can spend a token to make a strong move. there are also Situations, which players pick up and make moves from when you engage with those elements of the setting, and put down again when you're done. those all change between the games, though, so there wouldn't be much to put in an SRD style thing i think?
That txt demo of Exodus was precisely what I was looking for. Thanks a bunch. I absolutely see how, without context, there's not much in the way of mechanics to BOB.
EDIT: My copy of Dream Askew / Dream Apart just arrived last night. Woot!