The advance search option gives users the option to only show images that have been tagged with licenses like Creative Commons or GNU Free Documentation making it easier to find images that, legally, they are free to use on their blogs or webpages.
Creative Commons licenses allow the rights holders to further define how their images can be used. It’s possible to license images for general reuse, or for non-commercial reuse only. They can also choose whether to grant the right to change their images.
Personally, I think that if someone publishes a picture on the web then they have given up any rights they may have had regarding its redistribution. The web is a huge sharing portal and once a picture is published it is bound to be reused over and over again. If people do want their images to remain exclusive they should add a watermark or block image saving on it.
The new Google search options should suit everyone though. People who aren’t fussed about image rights can continue to search for images the usual way and people who do have concerns can use the new functionality. Everyone’s a winner baby.