Sybase conquered!
I finally got Sybase ASE 15 installed. I used CentOS 4.3 under VMWare Server beta 3 (also found how to disable debugging):
As root:
yum -y update (enabled centosplus and contrib)
sysctl -w kernel.shmmax=67108864 (also add line to /etc/sysctl.conf, this doubles the shared memory to 64K)
useradd -d /opt/sybase sybase (creates a sybase user and sets its $HOME)
mv /usr/lib/tls /usr/lib/tls.bak (stops Sybase linking against the wrong Kerberos libraries)
As the newly-created user sybase: