Dear Stefan & co,
Just to answer your final question as to why we want to call Julia from C (or Fortran): It is essential if Julia libraries are to be used with existing scientific codebases. One does not always have the luxury of declaring that Julia be the top-level/driver language 
If I am to write Julia code, Fortran users need to be able to call it, just like we’ve had C-Fortran interoperability for decades. (With MATLAB, this cannot be done, driving my move towards Julia.) I have a set of minimal demos of this task on github, but I’m finding it a challenge:
What I’m really missing is a set of @cfunction usage examples with arrays. Any pointers (pun indended) welcome
Best wishes, Alex