How to protect your development?

Question

PHP

Created a small project with an admin panel for a narrow circle of clients.
I would like to sell it to them for a small fee. But I would like the project to work only after payment.
Those. I would not want the client who bought it to be able to "easily" distribute what I wrote.
In what ways can this be done? In which direction to dig? Please add tags for google.

Answer 1

saas.
no other way.

Answer 2

Here is an old article that seems to be already , but it will prompt the necessary thoughts.