I wonder if selling integrations with language server[1] implementations would be a way to multiply the customer base enough to make this viable as a business.
If indexers were to be maintained separately, the only thought I have is something based on an IDE like Eclipse or IntelliJ, or something based on SourceGraph. To that end, I think open sourcing will do more to support usage, and usage would drive further licensing/support...
It’s possible there could be add-ons sold to help refactor code or maybe a web-based version, perhaps merging with SourceGraph as a client? Or use in code review? Lots of possibilities, perhaps, just not easily/quickly commercial I would think without further development first.
[1] https://github.com/CoatiSoftware/Sourcetrail/issues/750
[2] https://github.com/github/semantic