tobias_platen's blog

Mac OS X is a non-free operating system! This means it takes away your freedoms to use, study, share and improve the software.
Some people try to claim their freedom back by installing Mac OS X on a PC, ignoring the EULA and breaking copyright laws.
This is possible because the kernel of Mac OS X is free software under the Apple Public Source License. The DRM used to lock Mac OS X to Apple Hardware is described in the osxbook.

Mac OS X is based on the Mach kernel and uses components of FreeBSD,NetBSD and GNU. The Hurd, GNU’s kernel, is based on Mach 3.0. Before Mac OS X was released, Apple has contributed to a free software project called mkLinux.
The Mach kernel was ported to the PowerPC platform and used as a base for Mac OS X. Apple released Darwin under the APSL which is a free software license. Mac OS X without its non-free GUI is Darwin. GNU-Darwin was an attempt to help Mac users to enjoy the benefits of software freedom. GNU-Darwin replaces the non-free GUI with X11. Ironically the Bootable Installer CD of GNU-Darwin includes proprietary drivers.

The Mac OS X Internals book describes the architecture of Mac OS X and Darwin. GNU/Hurd is not mentioned in the book, but it shares parts of its architecture with Mac OS X. FreeBSD is used as a reference implementation by Apple. Most free operating systems ship with Webkit, CUPS ,and Grand Central Dispatch. Cocoa Programming on Mac OS X, Second Edition by Aaron Hillegass has a chapter about GNUstep and can be used with only free software. Both books can be used as a starting point for a free operating system compatible to Mac OS X.

UTAU is a non-free singing synthesis software that can be used only on Windows.Most music made with UTAU is more or less free and created by users. Some Vocebanks can be used on the Mac, but this platform has the same problem, that Windows has. Even if UTAU runs on GNU/Linux using wine with a patch, it wont be usable in a fully free distro.

So the only option is to rewrite a free replacement for UTAU from scratch. I’ve written a GNUstep based frontend for the Festival Speech Sythesis system. You will find the sourcecode at Google Code

This example also shows that it is possible to port Mac OS X Apps to GNU/Linux using GNUstep.