Appreciate the quick response! Unfortunately, no luck on this one:
[root@galena tmp]# yum --disablerepo=updates --installroot=/opt install joe
Error getting repository data for updates, repository not found
Further digging reveals that $releasever isn't getting set.
Running yum without --installroot set seems to work fine.
UPDATE: Well, despite numerous examples of "yum --installroot=yada" in the docs, this doesn't seem to work on a stock CentOS 4.4 install, and I've not found an adequate solution other than to install from source. My suggestion to those with this problem is to not waste time with it if you can install from source -- your time will be much better spent than trying to track this one down. Thanks to reddazz and Lenard for the suggestions!