First off, you need to try installing with a newer update of RHEL4 than what you've got. The 2.6.9-5 kernel that you're trying to install with is the GA version, and that is over TWO years old!! It most likely doesn't even contain the necessary NIC driver version that supports the adapter.
In fact, Red Hat doesn't support any version of RHEL4 on the DL380 G5 below Update 3:
The current update version of RHEL4 is update 5, so, I suggest installing with that version. If you have a paid support subscription with Red Hat, you can download the Update 5 isos from rhn.redhat.com, burn them to discs, and install the OS. You'd certainly save yourself a lot of trouble...
Hope that helps.
Also, the method that you're using to install the driver src package doesn't make much sense...if you're trying to install it with system-config-packages, then that won't work.