Hi,
I managed to install Websphere 5.0 (with fixpack 2 and cumulative fix 12) on a CentOS 4.1 (RHEL clone) and it's working without problems. Because of the 2.6 kernel, after you install Websphere, you need to put the following lines in ...AppServer/bin/setupCmdLine.sh somewhere at the beginning of the file:
LD_ASSUME_KERNEL=2.4.9
export LD_ASSUME_KERNEL
if you look in the LaunchPad.sh script from the Websphere CD for Linux, used to install websphere, you will see that this lines are in there.
Right now I'm trying to install Websphere on a SLES 9.2.. and I can tell you that I have some serious compatibility problems :-) Some of them were solved after installing Service Release 8 for IBM Java 1.3.1 (I installed it after I read a thread on a forum regarding compatibility problems with WAS 5.0 and RH 3.0 which were solved in IBM Java SR5
).
So, basically, if you want to be on the safe side, you should choose a distribution/version officially supported by IBM for WAS 5.0.
Have fun,
George