In a word... No. Linux is however, which is close to OS X, but is you wanted the source code from Apple, you aren't going to get very far.
OS is an open-source operating system
LINUX and Unix OS is open-source operating system.....! but Windows version OS is not the open-source operating system....!
Unix is NOT open source, it is proprietary copyrighted code owned by AT&T and you must purchase a license to use it, as you do on Windows and Mac OS X.However both Linux and GNU are open source OSs with equivalent functionality to Unix.
Having the source code open for anyone to edit or modify for free.
Symbian OS