That's a nice free tool to discover subreddits related to one that you already know about, and the map is pretty cool too!
However I'm pretty sure it doesn't let you search conversations on Reddit, categorize threads in ways that could be useful to founders (pain points, solution requests), get notified of conversations related to your business, or show you the growing categories of communities.
If you find a free tool that does this, I'd love to see it!
honestly it could be useful for the OP... and you never know how big the market is like for some of these services (perhaps they can build on that OSS project)
But I use this open source project https://anvaka.github.io/redsim/ for that purposes.
Unless there's something else I don't see here, i think this open source thingy gives all you need.