They were actually designed by Anton Kumaigorodski, creator of BLW and SBW, the two best Lightning wallets ever made.
And there is a spec here: https://github.com/lightning/blips/blob/master/blip-0017.md
Gm nostr:npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6 (and nostr:npub1rvg76s0gz535txd9ypg2dfqv0x7a80ar6e096j3v343xdxyrt4ksmkxrck )
Thanks for making hosted channels a thing (actually thanks for this whole suite of tools and ideas). I think these make a comeback 
Discussion
Thanks, I was looking into this. I think you all were ahead of the times.