Despite being one of the most tightly controlled technology companies on the market, Apple has a surprisingly complicated relationship with open source. Both of Apple’s flagship operating systems, OS X and iOS are based on Darwin, which is in turn based on FreeBSD. Apple has also contributed a large amount of code back to the open source community, most notably WebKit, which is used as the browsing engine in nearly every mobile platform. Considering the recent popularity of Apple’s systems, and since there was a big Apple event happening today, their involvement in open source is worth a look.