I said this already in another comment, but for this reason I think a crowdfunded campaign with a bounty that Adobe can use to cover their costs would be more likely to succeed than a simple petition.

Such a campaign could also send a much stronger signal of how badly people actually want an open source flash player. Starring a repo is too easy; it's better to let folks put money where their mouth is. Imagine if the hypothetical campaign raises a million dollars. It'd be hard for Adobe to ignore.

I assume it's patents that comprise the licensed technology? Does Flash contain code that has been licensed from other companies? If it's just patents, there's no problem in open-sourcing; on the other hand, I can see licensed code being a problem. But with all of the open-source implementations various codecs, gutting out the parts of Flash that contain the licensed code, and open-sourcing would be a viable option indeed.

It's been years, so take this with a truckload of salt, but if I recall correctly the issue was licensed code, along with a mostly ad-hoc structure of the player which meant extracting this would be difficult without a total rewrite, which is hard enough as is to justify but probably even more so when there's no clear business incentive for it. As well, a rewrite means considerable risk to breaking old content, which Adobe (and before them Macromedia) worked pretty hard not to do. I can see why this wasn't very palatable.

As I said though, it's been years and I'm just relaying what I can recall so I may very well be getting things wrong.