I am in charge of setting up a gis web portal and one of the functionalities would be to harvest some metadata from metadata servers like Geonetwork. I have been thinking of using Geonode because I have already used Geoserver. Apparently Geonode uses Pycsw to publish metadata but I can't see whether it allows to collect metadata from other servers and how? Is it possible to do it through the Geonode interface?
You can harvest directly with pycsw:
I am not sure if GeoNode has some UI to configure this, you should probably ask on geonode's mailing list directly. Although, depending on what is required, probably installing directly a geonetwork will be better for your needs.