[=MonsOlympus;690896]
Engine source code is not the same as Plugin source code, the reason it works on every version is because Epic provide the compiled Engine free, a Plugin still needs to be compiled for that version to see an associated Blueprint node if its not Engine level.
If you’re so concerned with trade secrets though I would recommend not selling at all, compiled code can be reverse engineered too with the right know how so there isnt really much of a black box. Thats how I see it though is if your competitive advantage in the form of algorithms is so important its in your best interest to keep it inhouse and this is probably why some AAA studios opt to use inhouse tech over Unreal Engine 
[/]
I always thought source code and plugin code are using the same classes and environment) You won’t RE if it costs more than price on marketplace. And this is my only concern. Why do you need to buy stuff that is already known to you through public source code?