I installed it under Trac 0.11.2 and it seems not to work properly, at least not with Firefox 3.0.3 under Ubuntu Hardy.
The flash itself is starting but the Freemind viewer isn't loading.
I checked the resulting source code (after the Javascript does it's work) with the Firebug plugin for Firefox and I found that all links start with a double slash '//', i.e. the SWF is linked to //chrome/freemind/swf/visorFreemind.swf, but also all other URLs like the one for the actual Freemind file, the CSS file, etc.
After removing the second slash with the Firebug edit function the visorFreemind is finally loading, but without loading the mindmap (which seems to be an other issue).