Luminotes makes heavy use of a browser feature called DesignMode to implement WYSIWYG wiki editing. Unfortunately, DesignMode support is incomplete in some browsers like Safari. Newer versions of Safari will feature improvements in this area, so look for Luminotes to support Safari at some point in the future. Recent versions of the Opera web browser do support DesignMode, so that's also a potential future addition to the list of supported browsers.
Please note that since DesignMode is only used when you're editing a wiki, you don't have to worry about DesignMode compatability when you're in read-only mode and just viewing a wiki. So Luminotes should work in read-only mode with just about any modern browser with support for JavaScript, cookies, and remote scripting.