Visual Editor does't work, solution: Edit WPG2/G2IMAGE/LANGS/xx.js
Change: tinyMCE.addToLang to tinyMCE.addI18n
Now, it's works.
The warning/disclaimer is a little ambiguous. Does it mean that you are working on Gallery3 and don't have time for WPG2 or are you working on a Gallery 3 version of the plugin, ie WPG3?