Dear eleysanne,
this is exactly the right location to ask these questions! However, I can't quite figure out what the issue is. When I run the example script, and re-direct the output to a file, I can open the result in Firefox 2.0 (osx intel) no problem. Other tools known to work are Illustrator, the adobe svg viewer browser plugin (for internet explorer, for example) and the batik svg viewer/editor. Either should show a three-tip additive tree with curved branches and a scale bar. What, specifically, is the problem you are having?
Best wishes,
Rutger Vos