You could just use a spreadsheet. The reason I pay for cap table management software is that it’s the easiest way to get a 409(a) valuation, which is something pretty much every US startup needs annually and open source couldn’t replace.

(I looked at getting a 409(a) valuation separately and the best prices were more than cap table software that bundled one.)

Let's do it and call it Cartb

spreadsheets

I would not trust the open source community with this private data. the potential for abuse is too distributed without practical access controls.