I'll see if I can find a simple package for you to get started on in the
mean time. Mario, Sébastien, would you have a simple package for
Alexandre to begin working on?
I have had a look at 3D Slicer, and its build instructions seem well documented (though the build process is quite slow):
As far as Orthanc is concerned, I am working on a development package and on a FUSE filesystem, but it is still WIP (expect nothing before, say, November). Maybe you could also help Mario in porting the Orthanc package to RHEL and CentOS via EPEL?