Earlier quoted context omitted.
There are several open source player implementations, but they're quite incomplete so far: * Lightspark http://lightspark.github.io/ * Shumway http://mozilla.github.io/shumway/ * Gnash https://www.gnu.org/software/gnash/
I used to work at a company called Spaceport.io (now defunct) where we had a nearly complete implementation. It included an impressive GPU-accelerated renderer and an optimising compiler from AS3 to JavaScript—we could run on mobile, desktop, and even WebGL, and do neat things like update over WiFi instead of USB during development. It was intended for Flash game development , and worked pretty well for that purpose.…
" neverending treadmill of having to implement obscure features that they didn’t even know they were relying on,"
I been coding emulators for fun (i.e. NES, Scratch) and it's been an interesting journey with all the gotcha's involved - however I don't think I have the motivation for any flash based ones, the only exception I've worked on my scratch2apk emulator (javascript) which has plenty of games going for it!