The lead developer is a Newgrounds employee (Mike Welsh) and is the author of Swivel [2], a Flash to video converter already in use on Newgrounds. They're targeting both browsers and the desktop with Rust and WebAssembly, and it can already run most basic Flash animations I've tested.
I personally am very excited, having grown up in the Flash era of the Internet, where everything from online coding languages (Scratch) to authors' websites (J.K. Rowling, others) to games and webcomics (take your pick) were made in Flash. Flash was such a universal medium that there's still significant amounts of our Internet history that nobody's converted - or been able to convert - to HTML + JS. And even then, many conversions are buggy and lacking in functionality. Having something like Ruffle available as an extension or a wrapper for legacy websites would be incredible.
If anyone's interested in Ruffle's roadmap, it's available here [3].
[1] https://github.com/ruffle-rs/ruffle
Newgrounds (sponsoring development of Ruffle) are already using Ruffle on some of their flash content.
The attempts at building something compatible like shumway have all been rather unsuccessful.
Even if the code was available, porting it to WASM would probably be a pretty big task.
It would be great to retain access to the huge amount of flash content out there though.
It's possible to play "Prince of Persia" in the browser (through DOSBOX recompiled to Javascript).
It's even possible to play the original Windows 95 (!) Pinball in the browser. Seeing the Windows 95 cloudy boot sequence in a Javascript canvas is disturbing. The game isn't as smooth as native, but it's definitely playable. ( https://classicreload.com/win9x-3d-pinball-space-cadet.html )
Alternative proprietary implementation was rather successful for game development. Sadly Scaleform GFx is now discontinued too and obviously we'll never see Autodesk publish anything under open source license.
This shows we should only allow technologies on the web if they have a clear path to preservation.
I think a similar thing should hold for DRM'ed video. Such videos may be supported on the web, but we should demand they lose their DRM when their copyright expires.
Between GNU Gnash [1] and Lightspark [2] one should be able to run quite a few of those (non v10) Flash programs.
[1] https://www.gnu.org/software/gnash/ [2] https://lightspark.github.io/