* There is no such thing as a "package sponsor". We use the notion of "sponsoring" only for CVS access.
* For a new package you need somebody, who _approves_ your package explicitly by posting a message to fedora-extras-commits list. Explicit approval is necessary before a new package may be built.
It need not be your CVS account sponsor to approve your package. It must be somebody with Fedora Extras CVS access and, for instance, could also be your package co-maintainer.
Preferably (in my point of view), the approval is posted before or shortly after the new package is imported into CVS, but must be posted before a first build is requested.