Yes, this is one of those horribly cross-posted mails that keeps Jo up
at night 
I have made a stab at some usage guidelines for our logos and such, but
in doing so I've realized that (1) I am totally unqualified for the
task, (2) it's a much bigger job than I had anticipated, and (3) it is
likely to result in lots of mailing list traffic...
I humbly submit myself to the Board and my Peers for further guidance.
http://wiki.osgeo.org/index.php/TrademarkGuidelines
-mpg