John,
We do not currently officially support our GPIB driver on RHEL 4 because we did not test the 2.3 release on that distribution. I have heard of others having problems with RHEL 4 and our driver, but I cannot tell you conclusively that it will or won't work. Your best course of action is to try to borrow some hardware and try it for yourself after downloading the NI-488.2 v2.3 for Linux driver.
Sorry I couldn't be of more help.
Scott B.
GPIB Software
National Instruments