In TUV-el5 installonlyn is part of their base yum package so they don't need it in yum-utils... Of course SL's yum package isn't the same as theirs so the SL50 systems just don't have installonlyn from either... The package I made simply lifts the installonlyn.py (etc) from TUV's yum srpm, cos that was easier than adding it into the SL yum (from my point of view anyway!)