Why not? The JRE was a free download for end users anyway, and open-sourcing it removed a large source of bad press. If Java was open-sourced earlier, it might have seen more adoption by hackers, and innovation. Now, it's an "enterprise" language, which basically means it has entered the "legacy" stage of its lifetime, and will go the way of COBOL in under 10 years.
That's a silly question. I am a computer conservationist proud of a growing computer collection. Of course I would, just for the kick of it!
I would like, of course, to run it on an IBM /360, or, if that were not possible, an emulator. You would access it via your own 3270 terminal. It would be made to look specially cool on 3290s - wouldn't be hard: anything looks cool on a 3290. I would develop it while wearing a white lab coat.
A Burroughs B-series would also be considered ;-)
Now, seriously, no. I wouldn't start a new product (I can conceive lots of maintenance projects done in whatever was already done to maintain code commonality) in COBOL.
And yes, you would have a hard time convincing me of starting one in Java too. I cringe even when someone proposes one in PHP.