Sparkle was around in 2006 - before the iPhone, before the Mac App Store. The original author ( Andy Matuschak ) worked at Apple for a number of years after Sparkle was being fairly well used.
I worked at a startup back in 2008 - we loved sparkle. Our entire app was ultimately stolen by Apple and implemented in iPhoto. We made the mistake of hiring an ex iPhoto team member as a contractor who ended up going back to Apple with our ideas. Wild time for startups.
See https://sparkle-project.org/about/