I'm a light user of Keybase and used it primarily for validation & signing. The social identity verification was quite nice. It seems that's what most of the users here were using it for.

My suspicion is while we're not likely to see much new development from Keybase, the existing capabilities aren't likely to go away for some time.

The premise of validation/signing isn't a technically complex approach and I'm sure someone can create and FOSS it. The question however is - what features would you want integrated and what things did you find annoying?