To uninstall RadLab, you'll need to remove a few files by hand.
1. Open Finder and navigate to the Applications folder. For each Adobe Photoshop item in Applications, open the Plug-Ins folder, and delete the Totally Rad link.
2. Also in the Applications folder, delete the Totally Rad folder, which contains the RadLab program itself.
3. (Optional) - If you're comfortable using Terminal, you can remove your recipes and other data as well. This data is stored at ~/Library/Application Support/Totally Rad, and you can remove the entire folder. This folder isn't accessible through Finder.