It depends on which technology the game is built on. If there’s already a mod for that technology that includes the binder and EDI integration, copying it is relatively easy. For example, there are RPGs made in JavaScript, like this one. If the game you want to integrate is also built in JavaScript in this particular framework, it will be fairly straightforward, replicating the mod integration will be quite simple.
However, if it’s built with another technology and no mod exists, then yes—it will be very difficult.