I'm secretly and slowly building a form building application. The idea is that in my association we don't want to rely on Google Forms. And we only want to use open source software. We are using FramaForms which is a bit clunky and doesn't have this feature that updates a spreadsheet automatically. I thought that I could just create something that would answer both concerns.

But a good open source forms app would probably change everything, I would gladly stop my small project (in favor of contributing to an existing one for instance). I see there is integration with a lot of products, including Google Drive and Google Sheet.

Would an integration with Nextcloud be considered?

Congratulations on open sourcing this, we need open source and self hosted form solutions. Critically private data is put in forms and that get sent to big private companies like Google, which is not ideal.

As other commenters say, you might want to use AGPL indeed, but I guess you carefully thought this decision.