For OEL4 download: https://oss.oracle.com/projects/yast/files/el4
For OEL5 download: https://oss.oracle.com/projects/yast/files/el5
For OEL6 download: https://oss.oracle.com/projects/yast/files/ol6
For SUSE Linux9 download: https://oss.oracle.com/projects/yast/files/sles9
For SUSE Linux10 download: https://oss.oracle.com/projects/yast/files/sles10
If you have installed them and it doesn't work try the console version of YaST by printing: yast2*
But sometimes it starts graphical version.
Or just switch the names for */usr/sbin/yast* and */usr/sbin/yast2*