Presumably FurBB is deployed somewhere. Definitely keep that URL to yourself. Feel free to link from that instance to the project, though.
Meanwhile, change the branding on the project. Even the backronym may be too risky.
Next, use the software to deploy a 2nd site that is more 'vanilla' which employers won't object to. Perhaps pick a hobby that some of the PHBs at your company indulge in (golf, fishing, etc.)? Or perhaps (depending on the market you're going to try and get work in), fixie bikes, pour-over coffee makers, hot yoga, etc.
Heck, start a side project that does forum-hosting using your software... You'll learn even more that way, and the instance that was the primary instigator can just hide among the multitudes...
This may still be too close to provide plausible deniability, but perhaps 'FurbyBoard' (literally a board about and for Furby enthusiasts, rather than Furries)
I think this question should have been "Ask HN: Should I hide my participation in furry fandom from future employers". You list a lot of technical points and features about your project, but it doesn't seem like those have much to do with the question: you could have written it closed source and in Haskell, and the question would be the same.
To answer that question, "do you want to work somewhere where you are required to hide part of your identity?"
This is a good idea, though. :)