I solved the problem and edited this post briefly to present problem and solution.
System: OsX 10.9, Diablo 2 LOD 1.13d, PlayOnMac 4.2.5, XQuartz 2.7.7
Problem: Installing the runeword mod, after installing Diablo 2 and LOD 1.13d to be able to use ladder only runewords in single player.
You should now be able to enjoy RVM and with this ladder only runewords in singleplayer!
cheers - ZodSonic1
Edited by ZodSonic1