license and copyright

The code needs a license and copyright. I would like to use GPLv3 for the license. Caltech wants copyright for all code developed by employees. Obviously GWINC has been developed by many people, most of whom have no association with Caltech. Unfortunately MATLAB gwinc does includes neither license or copyright.

I suppose we can email all authors to ask for their permissions to use a particular license. I have no idea how copyright should be assigned. Open to suggestions.