When I say "simple check" just create a hash for the game session, and if youre playing a multiplayer game - check the session hash, if they match, they are using the same license.
Else, play along.
Why?
Obviously it'd nice if you could, but there's no reason why a publisher should give up sales to people who buy a game multiple times just to make your life more convenient.
Found the MBA
https://www.youtube.com/watch?v=9h9wStdPkQY
(although he does have a pretty cool site: https://ooer.com/ - so I'm sure he cant be all bad... :-)
But how do you handle tracking purchases across even Steam, whatever Windows gaming store Microsoft has, several generations of Xbox, several generations of PlayStation, a few different Nintendo consoles, Mac App Store, iOS/iPad OS App Store, GOG, Epic Game Store, itch.io, etc?
I support the idea but it seems like a very difficult thing to keep track of, and I suspect every one of those stores wants some money too.
Sounds simple - but hard.
I should, within my own hom, play the game on any device.
I have 5 high-end machines/laptops, a ps5 xbox, ps4, tablets and phones...
If I own a license - I should be able to play from any of these.
If I join a multiplayer game that is OUTSIDE my LAN, then do a session ID check - and if two+ clients connect to game...
Make sense?
Something like fortnite, once you purchase the battlepass/skin on one platform they are linked to the account and available across all the other platforms the game is available on.
This model essentially poses big challenges with physical media and game preservation. Puts the user at the mercy of the publisher.
IIRC Ubisoft pulled the plug on "The Crew" which is online only at the moment and is scheduled for deprication March of this year!
With regards to physical media, I think the game can skip the licence check on the account itself for the base game if it was launched from a disc/cartridge.