Can a source code be shared and secured form unauthorized use at the same time?

Question

We have developed a script that generates certain reports as output. Input data being confidential in nature, one of our clients wants the code to be hosted in their country and also for the business continuity have access to the source code with a caveat to never re-use or sell it further.

I would like to know is there any process or technique say like a password or encrypted key that can be used within the code to prevent any unauthorized use of source code without us generating those keys to be inserted in the code.

We use python/flask on linux for our development purpose.

Answer 1

No there isn't

Atleast, there is no foolproof way. If you give them the code, they can do whatever they like with it. If you attempt to include some checks in the code that prevent anybody else from using it without having a password/key/etc, with enough effort, the check can be removed from the code by anyone copying it.