Service key check against project paywall

For the basic idea, go this way. Otherwise, read on.

The idea is to check against a customer's account or a master database or equivalent to see if they installed the game from an officially-sanctioned provider (itch, Steam etc.) and react accordingly by either locking down the game or playing pranks at the customer's expense, possibly even with a "last laugh" element similar to the infamous "endgame code exception throw" (specifically the one which simulates the SNES equivalent to the accursed BSOD while also running a complete data wipe in the process).

As this is likely to involve a script for the implementation phase I am posting here to see what any of you can do in this respect.

and HOW (technically) do you want to check that?
What is the specific difference between the installations that the plugin should check for?

I can already tell you that you'll never be able to do that in case of Steam, because Steam has its own DRM server and they will not give anyone access to it (because anyone with access to that data could try to circumvent steam DRM with that info). On the other hand if you go by steam they'll just tell you to let them handle it, so no need for that. That is what you pay steam for by their % of the sales after all.

EDIT:
Just to make it clear: the only technical way to handle this is to have a DRM server storing all customer data to be chacked against.
And in that case you need to tell the plugin programmer what formats that server uses - you'll never get someone to program a DRM server for you for free as that is too much work.

And providing that info about the DRM is usually against the EULA of a purchased DRM server, so you'll need to think about how you can give that information to someone thrustworthy in a way that is cleared with whoever programmed the DRM server.