Allows users to use the [gallery] shorttag with link="none" in order to have an image gallery with no links. [gallery link="none"]
Other plugins that affect the [gallery] shorttag may overwrite this plugins capability to apply the link="none" functionality. Try disabling other plugins and test again.
You will need to insert a Gallery as normal, and then switch to the "HTML" tab of the page/post. Find where the editor has inserted the [gallery] tag and make sure that link="none" is within the [gallery], i.e. [gallery link="none"]. Be sure that there is only one entry for "link".