gkrellm-freq's specfile has "License: GPLv2", but actually I think it should be "License: GPL+" because I don't find anything saying specifically GPLv2, and the GPL text itself says that if no version is specified, any GPL version goes. http://fedoraproject.org/wiki/Licensing agrees. Additionally, I'm just about to build gkrellm 2.3.0 for EL-5 in EPEL (no plans for EL-4), so this package could be built for it as well shortly.
You're right. I had misunderstood, and thought that if no specific GPL version was mentioned and the GPLv2 text was included, then the files would be GPLv2 only. I'll need to fix this in a few other packages too... I'll go ahead and change it for gkrellm-freq and rebuild an EL-5 package.
The package finally rebuilt for EL-5, yay!