This extension was supposed to be a commercial product. But due to time constraints I've after four years decided to release it as open source in order to prevent it becoming vapor ware.
It doesn't contain all the features originally intended in the product plan but the project is available on BitBucket under the MIT license for anyone to improve.
Forum thread where you can discuss and ask for help: http://forums.sketchup.com/t/bezier-surface-editor-is-now-open-source/4208
Menus & Toolbars
- Draw » Bezier Surface
- View » Toolbars » Bezier Surface
I'd be happy if you donate a cookie (or a beer) if you find my plugins useful.