* Lightspark http://lightspark.github.io/
* Shumway http://mozilla.github.io/shumway/
* Gnash https://www.gnu.org/software/gnash/It was intended for Flash game development, and worked pretty well for that purpose. Unfortunately, we spent a lot of time dealing with large customers who wanted to use it to port existing Flash games to mobile, which was basically a neverending treadmill of having to implement obscure features that they didn’t even know they were relying on. :/
Parts of it have been open-sourced, but I wish the parent company would just release the whole thing. Last I knew, there was one guy maintaining it for one customer after the main engineers were acquihired.
" 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!