You can see how the image search box within Google Docs works below and I have highlighted the small note explaining the license.
This is of course just one small part of a process of understanding attribution and content usage for students but could be an important little tool for teachers and pupils. Once an image is selected it shows you the website that the image has come from.
Google explain a little more about this change from the Learn More link you can see in the images, saying:
When using the Google Image Search feature in Google Docs, your results will be filtered to include images labeled with a license that allows you to copy the image for commercial purposes and modify it in ways specified in the license. Only select images that you have confirmed you can use legally in your intended context, including with appropriate attribution if necessary.
Once you Select the image it is inserted into the document without an attached link or attribution. This is still a step students will have to do manually which is actually a good thing.
Unfortunately the image search and subsequent filtering shown in this post is only in Documents at the moment and not in Presentations which would be really useful. No doubt things will become more consistent soon.