Following this thread http://www.3dconnexion.com/forum/viewtopic.php?t=280, I wrote a very primitive proxy that translate motion events from the cocoa SDK into Xevents, compatible with the legacy spaceball unix SDK.
I really don't know anything about X11 or cocoa programming and can barely write C (I'm a fortran90 / scientific computing person), so I can garanty that the code is ugly, but it does its job.
If anybody is interested in having a look at the code (it is hosted at http://www.math.lsu.edu/~bourdin/Files/MagellanProxy.tgz ). A very simple program using the X11 bindings (shamelessly taken from the old unix SDK) is at http://www.math.lsu.edu/~bourdin/Files/xapp.tgz
I am stll a bit puzzled about the signature and name values in main.c . I pulled them from the example in this thread http://www.3dconnexion.com/forum/viewtopic.php?t=232 without really understanding.
Have fun with the code.