People that trusted them deserve the bad taste. Don't expect them to lift a finger toward open source, they won't and expectations that there was even a chance is another over-extension of entirely unearned trust.

I think I saw something a while back that said they don't want to because they built a bunch of proprietary framework stuff that they want to keep for themselves cause they still use it in Dia.

Since it's a client app someone else could open-source it for them instead.

yeah that would be the absolute best possible thing for them to do