Nonparametric Tukey-type multiple comparisons "Nemenyi" test

I am trying to do a Nonparametric Tukey-type multiple comparison 
post-hoc test to determine which groups are significantly different.  I 
have read the dialogue on this topic from the R-help, and am still not 
clear why no statistical packages include this test as an option?  Is it 
not an appropriate test to conduct on non-normally distributed data?  Is 
the only option to calculate it by hand using the (Zar 1996) formula?

Thank you in advance for your help.

Rikki Grober- Dunsmore
National Marine Fisheries Service
National Marine Protected Areas Center
110 Shaffer Rd.
Santa Cruz, CA 95060
831-420-3991 


Unless someone like you,
Cares a whole awful lot,
Nothing is going to get better,
It's not.
       - The Lorax, by Dr. Seuss, 1971