Is it possible to create an own obj-C Cocoa Touch framework which can be used by other developers? And furthermore can you protect this framework?
You can create a static library. There is an option in the XCode project chooser to do this. You'll have to distribute the compiled static library file and the header files to users of your library. Your actual implementation files (.m) do not need to be distributed.
GHUnit does a good job of this - packaging up the libraries for both simulator and device - so I recommend looking at this project. (I also recommend using this library for unit testing :-)