It seems that the thing you want to do is not possible. I had a quick look at the code, and indeed whether the forum is displayed "collapsed" or "expanded" can only be chosen for users that are logged in. Maybe Jason can add a "forum_default_view" option for the next release.

As a workaround you could change the links in the "category_list.html" template from

gforum.cgi?forum=<%forum_id%>

to

gforum.cgi?forum=<%forum_id%>;<%unless current_user_forum_view%>do=forum_view_expanded<%endunless%>

or something like that (haven't tried this, but looks like it works!).

Ivan
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Iyengar Yoga Resources / GT Plugins