(Hello downvotes? It's true, we preserve all of those things through virtual machines of one variety or another. The Flash plugin doesn't magically stop working because Adobe stops developing it.)
Seems a weird thing to bring up for why we shouldn't opensource a runtime to preserve content....
And also, why do you care if some people _do_ want to continue developing Flash? It's going to get removed from browsers either way. The mere existence of a Flash player on somebody's desktop somewhere is not a security liability for you.
The argument presented was that open sourcing would allow that little bit of internet history to be preserved. My point is that you don't need source code for that. IMHO we don't want anyone to continue developing flash. Even it's creator has declared EOL for it. I understand there are people who want to mess around with it and do things that are potentially interesting, I object to disguising those desires as a preservation activity.
Just like with Java it's the Flash in browser that sucks, not Flash in and of itself.
Your reasoning about proprietary stuff is just plain stupid and made completely retrospectively. There is literally no reason why we shouldn't preserve this work just because some people don't see value in them.
People get permission to build Commodore 64 clones, for retro computing preservation, and Hacker News says that's great. Someone requests similar permission for Flash, and now we're upset about the notion of a proprietary codebase being open sourced? Why? Because Steve Jobs said it wasn't cool? Because you're seriously afraid that it would make a comeback, and dethrone HTML5 on the mainstream web?
Guys, someone started a petition to ask a company to donate a propriety codebase after EOL. That's all. This is just idle chat, because nothing in Adobe's history suggests that they would actually consider this.
Regardless, if you would rather NOT see a historically signficant codebase open sourced, then simply don't sign the petition. And take all the low-quality jokes and guffaws back to Reddit, please.