With completely wireless earbuds, the rule is: when the battery fails, they have to be disposed of. Not so with the Fairbuds, that allow you to replace batteries in just a few seconds. Combined with a repairable design, the earbuds should therefore have an extremely long lifetime.
This seems like part of their android os for FP5, TWRP is a common open source android recovery image: https://en.m.wikipedia.org/wiki/TWRP_(software)
I don’t know if it their entire OS, or just some components that they can open source