Unfortunately it’s implemented on top of std::set/std::map and I’ve had problems with heap blow up on large maps. This project looks like it uses 32 bit indices into a vector for backing store.
In the meantime, I have this impelemented in TypeScript in case anyone else will find it useful: https://github.com/ShieldBattery/node-interval-tree
Plus, the account of the one you're linking to only has that one comment in their comment history. So I think the shenanigans lie there