Why is SketchUp not compatible with OS X 10.3.9?

Some of the features added to SketchUp 6.0.514 require OS X 10.4.1 or higher. As a result, systems with OS X 10.3.9 or earlier won't be able to upgrade to a more recent version of SketchUp. If you have a previous version of SketchUp installed, we suggest you continue using that version. Please be aware that you'll be prompted every two weeks to update and download a new version. Disabling this prompt isn't available at this time.