Anyone who can read through your source code can make the program themselves. Someone would want to buy the service because they can't program nor read your code. Make it a guarantee if you think it is a selling point.
Mind you this would include DBs, servers to keep the data up-to-date, GraphQL servers to serve the data, etc. I guess it would be akin to the ElasticSearch model where one can set it up by themselves where for simple usage one would end up spending less time and money if they were to pay for my hosted solution.