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.
GPS is such a weak signal that almost anyone transmitting ground based signals on the right frequency could easily drown out GPS - and do spoofing with a little extra research. So theoretically you could spoof near a data center and mess up a lot of data powering 1000s of applications.
On top of this civilian GPS is made to be jammed and innacurate - there's a better one the military has moved onto because of this (see the m-code section: https://en.m.wikipedia.org/wiki/GPS_Block_IIIA)
So yes, relying on an easily jammed atomic clock hurtling through space seems like a bad idea... But it's kind of the best we've got right now. At least until the cost of putting your own satellite into orbit goes down.