I maintain a similar (but less popular) open-source CLI that generates flow charts for dynamic languages (Python, JS, Ruby, PHP) - https://github.com/scottrogowski/code2flow/
The thought has crossed my mind to try to actually sell it as a SaaS. But by itself, call graph visualizers are the sort of thing that you would need only once or only every once in a while. That sort of software is very difficult to monetize - as 10,000 failed productivity app companies could tell you. I don't know the details of what happened with Sourcetrail but I assume it was similar - developers might have found it useful occasionally but it's not something most developers would use daily or even monthly - so it's hard to justify a subscription.
The thought has crossed my mind to try to actually sell it as a SaaS. But by itself, call graph visualizers are the sort of thing that you would need only once or only every once in a while. That sort of software is very difficult to monetize - as 10,000 failed productivity app companies could tell you. I don't know the details of what happened with Sourcetrail but I assume it was similar - developers might have found it useful occasionally but it's not something most developers would use daily or even monthly - so it's hard to justify a subscription.