Subgraph provides a third party implementation of Tor called 'Orchid'. Since this is not part of the official Tor Project, how do we know that it can be trusted ?
The reasons for trusting (or not trusting) Orchid are the same as with Tor proper: Orchid is open source, so you (or anybody else) can audit/examine/analyze the source code.
One concern I would have with Orchid at the moment is that it doesn't seem to be a very active project. There are a bunch of bug reports/pull requests on the github site which haven't received responses, and there generally doesn't seem to be much development activity. It also has far fewer users than the main Tor implementation.
I would comment on Nathan's post, but I don't have enough rep. He's completely right. They offer the link to their Source Code in their download's section, along with a link to their Git Repo - https://github.com/subgraph/Orchid