Earlier quoted context omitted.
OK, so when the game starts up it needs to see some proof that you own a license for it. So it needs to see proof that you own an NFT. I am not aware of the technical details of various NFTs but I'm going to assume that you prove ownership similarly to how it can be done in Bitcoin--signing a transaction/message with a private key that corresponds to the public key of the asset in question. I would be happy to learn…
You prove you own the NFT the same way you prove to your bank that you have money: by letting the bank hold it for you. You deposit or lock the NFT into the service (essentially making it a staking contract ). This associates the NFT with an account within the service's smart-contract (of the depositor's choice), which can then be mirrored by an oracle-process observing on the service's backend to become "a record in…
I don't see what advantage this implementation offers though (happy to be wrong). The game is checking with Valve to see if I am allowed to play it. I will need Valve to agree to honor my token and talk to the game appropriately in perpetuity. A third party that I sell the token to would also be relying on Valve to honor the validity of the token after I transfer it to them. This has very similar characteristics as if Valve build out tools to sell/trade games using their existing database. Valve can decide any day to stop honoring tokens, maybe "locking" currently deposited tokens to your account by making the database record permanent and not caring about tokens any more.
Maybe the game has a facility to check with other services that also implement the staking contract, as sort of a backup in case Valve dies or as an attempt to be vendor agnostic? I think that has some interesting difficulties too.