Yes, I understand. But we've created a value that's too slow to grow. It doesn't make sense.
You don't seem to have a problem where open-source is the answer; the problem you seem to have is you built a business and a business model you weren't intending to build; and you don't solve that by open-sourcing. You can solve that a myriad of ways, but none of them are readily solved by open-sourcing your product.
Your product's website is very 'feature' oriented, and not very 'Pain/Dream/Fix' formatted. https://sharpen.page/jtbd/copywriting/pain-dream-fix-and-jtb...
If the business is small and profitable but it’s not growing how you’d like then I’d probably be more interested in selling it if it was me. I am not sure you will be able to sell it if the code is all open source.
Why? No grieving. Many products in the world are not growing as fast as their creators would like – it is OK. We just try new things and see what happens. Like what if you put all the code on the net :-)
Though, I like what someone else brought up in another reply to you about pain/dream/fix. It’s very similar to what you learn in programs like Force Management training where they teach frameworks like MEDDPICC. Finding business pain, demonstrating negative consequences to build urgency, etc.
I don’t know if this is something you’ve already done or if the sales approach has been more like “if you build it they will come.”