Since the effort started from some Italian developers/sysadmins, I would be surprised if dev-one wasn't a good approximation of the correct pronunciation. As an Italian, that would be how I'd pronounce it.

This is exactly the case, and people are being very US-centric about it, complaining about something which doesn't sound right to them, but which sounds perfectly natural to the original developers.

This is the right way to pronounce it:

http://danex.nexlab.it/devuan.wav