 In 1999, Apple announced it would release the Mach 2.5 microkernel, BSD Unix 4.4 OS, and the Apache Web server components of Mac OS X Server.At the time interim CEO Steve Jobs alluded to British naturalist Charles Darwin by announcing "because it's about evolution".In 2000, the core operating system components of Mac OS X were released as open-source software under the Apple Public Source License (APSL) as Darwin; the higher-level components, such as the Cocoa and Carbon frameworks, remained closed-source.