It looks like that the GNUstep environment is not loaded. Did you run:
<pre>
  source /opt/opengroupware.org/OpenGroupware.org.sh
</pre>
  or
<pre>
  source GNUstep.sh
</pre>
"decimalDigitCharacterSet" is part of libFoundation and located  somewhere in <tt>/opt/opengroupware.org/Libraries/Resources/libFoundation/</tt>  AFAIK.