As Royal Bg mentions in the comments, if they have the source code, there’s no way you can secure it against them making a separate copy. As you mention, any attempt at a licence key, or any other type of method, they’d be able to get around.
As Royal Bg mentions in the comments, if they have the source code, there’s no way you can secure it against them making a separate copy. As you mention, any attempt at a licence key, or any other type of method, they’d be able to get around.