Hi,
The pb comes from the silverpeas-postgresql-5.13.3-1.noarch.rpm package doesn't exit anymore in the repository.
Normally, yum would download the package silverpeas-postgresql-5.14-5.14-1.noarch.rpm for Silverpeas 5.14. I think the repo metadata were broken, driven to this misbehavior.
I've clean up the repo metadata (as well the silverpeas packages) and rebuild the packages for both debian and redhat-based distributions.
Try again to install Silverpeas 5.14 with yum.
Note: Linux Fedora 20 isn't currently supported;17 is the last version supported for Fedora.
Nevertheless you can try to install it under Fedora 20, but use instead the repo for Fedora 17
http://www.silverpeas.org/repo/rpmfedora/17regards,
Miguel