I don't think that's a good reason to switch to a non-AWS system, or make it portable to multiple systems. If they are paying you for your service then they wo

I don't think that's a good reason to switch to a non-AWS system, or make it portable to multiple systems. If they are paying you for your service then they would be willing to use AWS, even if AWS is proprietary. You don't need to open source your code. You can have it "source available", or have a clause in the contract that if the service is discontinued then you'll release the source code to your customers, or some other escrow scheme.