“I don’t think it would be long” is an age-old planning fallacy in this field, AI hasn’t changed that. It is certainly easy to clone a UI today because an agent has a target to iterate against, but cloning all the behaviours of the software in question is going to prove to be much more difficult.

These are decades-old software where even the inconsistencies, quirks and bugs are now considered features (because users have come to rely upon them) - a full detailed specification itself would be very complicated. My bet is this OSS-clone hype will last all of 6 months.