I will never again build any kind of workflow for my knowledge on top of anything that isn’t open source. 5y is a long time and 10y is an eternity for these sorts of products but its just a fraction of my working life. My own personal setup is a bunch of markdown files and it’s great, so I like that approach, but I’m very cautious about investing time for something so important in a product i don’t control.
We'll likely make a formal guarantee to open source in the case of us shutting down. Didn't realize that was a possibility, thanks for the suggestion!
The problem is the bankruptcy court/buyer/ex-spouse/whatever may have a different preference. So you may want to set up something legally binding now when everyone is the same agreement.
Could you also solve this by GPL+Commercial license for those that pay?