Steve Jobs has built a more successful Linux than Linus Torvalds, according to InformationWeek writer Alexander Wolfe:
Who knew that Apple's latest version of Mac OS X was knitted together from enough open-source software to give Linux a run for its money?... [I]t's astounding when you count up the number of open-source modules included in Leopard... For many of these, you can download an archive which includes deep technical information and/or source code.
Wolfe notes that the availability of the source code allows an enterprising developer to build his or her own "twist" on OS X just for the challenge. Unfortunately, on the flip side, it also gives malicious hackers a lot to work with.
While not all of OS X is public, the story says, there are many parts that Apple owes to outside developers -- not the least of which was the Mach kernel itself, on which the OS X kernel is based. This, Wolfe says, proves that the company
...[has] obviously figured out how to successfully build on the work of others, how to market that stuff, how to avoid internecine warfare and fanboy pointlessness. It also has demonstrated how to build a business where you can make real money.