I was a technical cofounder who built a company on Firebase+Stripe like you did. When we were acquired it was for the loyal customer base we built in a niche space, and the relationships we had painstakingly built over several years. The CEO of the acquiring company gave us valuable insight that the value of the code we built was not even a minor factor in the acquisition price/decision. Our first project at the new company was to migrate our customer data and backend to their infrastructure on AWS. Unless you have built something proprietary that solves a technical challenge in a meaningful customer-facing way, which seems unlikely based on your description, I would suggest moving on. Best of luck to you on future endeavors!
I had the same thought. OP talks about authored code, but then lists all the pieces that are glued together into a solution.
That takes some customization, but he's not talking about a software product, he's talking about what amounts to a professional services integration of several existing products. Consulting gigs like that can make you money for your time, but the end result is too specific to the situation with too few lines of original code to have much/any value.
If OP hasn't been paid for his work and it's being suggested this software is his pay, then I'm going to agree with other posters and say his co-founder is just dumping him and walking away with anything worthwhile, including the percentage of the corporation OP had which might be worth $$$$ or $0 in the future depending and leaving him with worthless code... and if there's a no-compete written into the sunset agreement for him, he probably can't even use the code, sell it, or consult with it.
A similar thing happened to us. The technology always seems great and innovative (and it is), but the moment a replacement is found, it becomes instantly worthless.
...and so it becomes a huge gamble to pay for technology that doesn't have an active an immovable revenue stream.
Indeed, recurring revenue and customer relationships are what gives a company its worth. It's the hard bit for lots of modern startups, which could be cloned by a couple of devs in a relatively short space of time.
