From Fedora Project Wiki
Historically, we have had a exception for projects where upstream development is led by Red Hat itself. They could just contain the source within the srpm and add a comment indicating that. However this is not a acceptable practise anymore since it hinders adoption and participation from the free software community including other distributions. Use a proper project hosting infrastructure like http://fedorahosted.org instead.
Rationale
This exception was added to the guidelines when it was common practise to have many of the Red Hat distribution specific tools not available as a source release separately and the only way to get them was to extract it from the source rpm package. However this is not a sane development practise and hinders cross distribution adoption and participation. Therefore, it is much better to drop such exceptions and recommend a proper infrastructure instead.