I've been blasting PeteJKim with DMs and @'s anywhere I can find him but I don't think he's going to open source it. It's a shame -- I had only just discovered Nitrous and switched to it when they shut it down. It really was the best solution.
Open sourcing the tech would probably take a ton of work, though. Probably a lot of proprietary tech. I wish they'd at least open source Nitrogen, the Atom plugin, even with missing bits.