from Apple's web Darwin Mac OSX Opensource Pages <http://www.apple.com/opensource/>
Mach 3.0 Kernel AND FreeBSD kernel (portions) 4.8 BSD FreeBSD libraries (libc) 5.0/5.1 BSD
It has been mentioned OS X doesn't use procfs UNVERIFIED
------------THIS May indicate Heavy Lifting required when bug hunting -----
-------------------------Very cross-port implemented-----------------
Mac OS X provides a robust set of optimized libraries, making it easy to port your existing UNIX code. For example, a standard, multithreaded C library (libc) includes support for such capabilities as reentrant variants of standard functions (such as strtok_r), facilitating the porting of thread-aware applications to Mac OS X. For applications that require non-Roman character sets, Mac OS X supports wide character datatypes (wchar_t and others). Panther also supports UNIX/Linux portability APIs, including System V semaphores, so porting applications from versions of UNIX such as Linux and Solaris presents no problem.
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Let's get a little more Accurate
External Open Source projects used by Apple:
Kernel / Libraries CCE's (e)fax 0.9a-001114 GPL Common Unix Printing System 1.1.19 Special dlcompat (dlopen/dlclose) BSD FreeBSD kernel (portions) 4.8 BSD FreeBSD libraries (libc) 5.0/5.1 BSD gimp-print drivers 4.2.5 GPL GNOME xml C library (libxml2) 2.5.4 MIT GNU libiconv 1.9 LGPL International Components for UNICODE (ICU) 2.6 MIT iODBC Driver Manager 3.0.6 BSD KHTML (WebCore), KJS (JavaScriptCore) 3.0.1+ LGPL ncurses MIT poll (shim on select) 1.2 BSD X11 (XFree86) 4.3 MIT
Scripting bash 2.05 GPL enscript 1.6.1 GPL expect 5.38.0 Public perl 5.8.1-RC3 Artistic apache_mod_perl Apache PHP (apache_mod_php) 4.3.2 Apache Python 2.3 GPL ruby 1.6.8 BSD tcl 8.4.4 Other tcsh 6.12.00 BSD zsh 4.1.1 MIT
Utilities bc 1.05 GPL bzip2 1.0.2 BSD
chess GPL curl 7.10.2 BSD diff (diffutils) 2.7 GPL dscl APSL emacs 21.2 GPL gnuserv GPL gnutar 1.13.25 GPL grep 2.4.2 GPL groff 1.18.1 GPL gzip (zlib) 1.2.4 GPL less 378 GPL screen 3.09.15 GPL srm 1.2.7 MIT texinfo 4.6 GPL vim 6.2 Public Networking / Security Apache 1.3.28 Apache apache_mod_ssl BSD BIND 9.2.2 BSD CAST-128 & Blowfish encryption 0.9.7b BSD Common Data Security Arch. APSL fetchmail 6.1.2 GPL IPv6/IPsec 20010528 BSD Kerberos for Macintosh 5.0 (krb5 1.3) MIT net_snmp 5.0.8 BSD ntp Public OpenSSH 3.6.1p1+CAN-2003-0693 BSD OpenSSL 0.9.7b BSD PAM - Pluggable Authentication Modules 0.76+ GPL postfix mail transfer agent IBM procmail 3.21 Artistic rsync 2.5.6 GPL SAMBA (SMB File sharing) 3.0.0rc2 GPL sudo 1.6.6 BSD tcp_wrappers Other tcpdump 3.6-cvs BSD xinetd 2.3.11 BSD
Server Apache httpd 2 Apache Axis 1.1 Apache Berkeley DB4 for OpenLDAP & Cyrus Sleepycat Cyrus IMAP mail server Other JBOSS 3.2.2RC2 GPL mailman GPL MySQL 4.0.14 GPL OpenLDAP Other SquirrelMail 1.4.1 GPL Tomcat 4.1.24 Apache
X11 for Mac OS X — Use legacy UNIX-based programs via the X11R6.6 X Windows display server integrated with Quartz compositor.
FreeBSD 5 — Use the latest commands and libraries from the popular FreeBSD distribution.
gcc 3.3 — Generate code using the latest C, C++, Objective-C open source compiler with optimizations for the G5 processor.
pstopdf command line tool — Convert PostScript Level 3 documents to PDF via command line tool.
Updated UNIX man pages — Learn system command line tools more easily with significant update to collection of system man pages.
Activity Monitor — Display processes, CPU, system memory, disk activity and networking status via new utility.
Improved Terminal Application — Use command line tools via Terminal, now with improved emulation and double-byte encodings.
Kerberized SMB, AFP, SSH, Mail — Use system services that support Kerberos single-sign on authentication tickets.
Latest Scripting Languages — Use the best tool for the job by selecting from a full collection of UNIX scripting languages, such as perl, PHP and Python, updated to latest versions.
_______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html