OK, I think everything is clear now.
When you add dependencies in Targets->neverball->Link Binary with Libraries, Xcode only add a "-lintl" to linker command line, if a library "libintl.a" is added. That's all, there is no reference to any file in particular.
BUT, you add a search path /opt/local/lib for MacPorts (and I add /sw/lib for fink, that's the same). Then, the linker will look for libs in this directory, so it will look for a lib called "libintl.*" for example. That's the problem: when different versions of a library is found in a directory, it takes the dynamic version first.
I fix the problem very easily: I remove the search path "/sw/lib" and check if all my libraries lib*.a can be found in external_libs of Neverball projects.
Try compiling without "/opt/local/lib" in your search path and see if it works. I'v juste tried that and I've got no more error, and Neverball binary is much bigger too...
If somebody else want to try my package you can get it here : [invalid, see below]
I hope I'm clear