Many people and sites have helped to gather the information condensed here. I'm not able to remember and list all of them, but this is a try:
- Instruction on how to use repos from openSUSE's build service by Patrizio Bekerle
- Instructions on how to compile the GNUstep frameworks with libobjc2 on Ubuntu/Debian by Patryk Laurent and a very helpful and extensive guide on compiling and installing by Andreas Fink
Special thanks to
- Fred Kiefer for numerous mails of patient help to understand and fix some bits and pieces and maintaining gnustep-gui (AppKit) of course.
- David Chisnall for creating and maintaining libobjc2.
- Riccardo Canalicchio and Alessandro Sangiuliano for creating the initial Rik.theme which was important to reach out for a good looking GNUstep next to the Nesedah theme from the Etoilé project (yes, that's been given up).
- Bertrand Dekoninck who did great pioneering graphics work on creating an appealing GNUstep working environment and GNUstep themes.
- Niels Grewe for writing DBusKit and DBusMenu - great stuff, hoping for more fixes to come!
- Riccardo Mottola for maintaing numerous GNUstep apps.
Generally speaking to the GNUstep community as a whole as there are many friendly and helpful people. Thank you!
- The GNUstep wiki
- a small GNUstep dev tutorial
- Cocoa Dev Central - Learn Objective C
- Cocoa Coding - as well a very good, free tutorials on how to code Cocoa/GNUstep/Objective C (in German, sorry)
Best books on Objective C and Cocoa development
- Aaron Hillegass/Adam Preble: Cocoa Programming for Mac OS X. 4th ed. Addison-Wesly, 2012.
- Holger Hinzberg: Objective-C und Cocoa Praxiseinstieg. Programmierung für Mac OS X und iPhone. 2. Aufl. mitp/hjr Verlag, 2012.