There are 3 people on the planet who can make changes to it and one person who can work on their custom made source control system. Single points of failure are not sustainable.
Having worked in Cedar Rapids there's really only 1 employer that makes up the "good job" pool - used to be called Rockwell Collins.
I'd guess there's a similar situation in most of towns on this list, which would mean living there is a huge risk unless you plan on working at the one or two companies in town for life.
I was expecting another company copying the core business logic based off the title, but it looks like things related to redirect and auth are very (very) similar.
Nearly every API is going to need solutions for these, and they all look very similar. I'd be surprised if the redirect and auth parts weren't at least in some way inspired by other APIs.