@shemmes There aren't too many good resources, there weren't too many back when Ostatus was created, and most of them are now lost. Here's a good overview: https://social.heldscal.la/url/337948. Here's the last standard draft: https://www.w3.org/community/ostatus/wiki/images/9/93/OStatus_1.0_Draft_2.pdf. There's also #socia on freenode and https://matrix.heldscal.la/#/room/#programming:matrix.heldscal.la where we also discuss ostatus / federation-related things.