[laurowyn]

Certainly an interesting one.

IANAL, but I believe the terms of the purchased license would be to use the product with only the license key provided. Therefore using an alternative key would be a breach of the license terms, meaning you're using unlicensed software and subject to all relevant laws.

I can see an argument that the vendor is in breach of contract by failing to provide a valid key with the license, and therefore the contract is void and the vendor should refund.

And yet again, I can see an argument that the license has been paid for, and a different key is used in the interim to access the paid for software, therefore no loss has occurred to either party rendering the whole argument moot.

Would be interested to know if this has been tested in the court system.

[heisenbit]

Depending on jurisdiction there may be rules or case law related to re-engineering and patching of purchased software to keep it working. This is again a reminder how important the right to repair is.