For those not familiar with OpenFL, /u/larsiusprime posted a nice summary of how it's used:
"OpenFL is is a programming API that mirrors the Flash API, but in the Haxe language. So you take your old ActionScript code and port it over to Haxe (very similar language, but with additional features). Then you also take your Flash-vector-art SWF files, and you load it with the Haxe SWF library. OpenFL ensures you can still make all the same method calls to the Flash API, etc.
When you compile, you select one of many targets, kinda like unity: C++, JavaScript, etc. It conveniently packages those targets up into special configurations like "Android", "Windows", "HTML5", "Linux", etc.
So you can take your existing flash code and art, but get it running NATIVELY, in say, Linux desktop, with no need for the flash plugin or AIR runtime -- it's just a C++ app that does the same stuff (and much faster!)
You can also output to HTML5 so your players don't need the flash plugin anymore (the HTML5 target is still fairly new).
As an end user, there's nothing for you to really do, except to wait for flash developers to switch over to it. From your perspective, all you'll really see is that instead of Flash apps on the web, there's more HTML5 apps. And instead of AIR apps for games on the desktop, they're natively compiled for Linux. What happened in these cases is that the developers were using Flash before but switched to OpenFL."