I have published paid app on Google Play and Samsung Apps, so I have used there licensing services in order to protect the game from illegal copying (DRM).
In order to use these services with my current AIR apps, I have developed by own ANEs.
The source code along with extensions and some usage examples can be found on Github: ANE License Checker
I’m also going to publish the game on SlideME, so will add support of their licensing service later.
Luckily, Amazon and B&N has built-in protection, that is applied when you publish your app, no need to make extensions for them.