Aaron Boodman, a Greasemonkey author and a Google programmer who's active in the Gears project, contributed Greasemonkey support to Chrome, and the Google Operating System blog picked up on the change.
At this stage, enabling Greasemonkey requires people to use a cutting-edge developer version of the open-source browser and to launch it with a "--enable-greasemonkey" option set.
Greasemonkey lets people run scripts that modify Web page appearance. For example, back when Google's Gmail service lacked a "delete" button, people could add one by installing the Greasemonkey extension for Firefox then downloading a particular customization script.
Google wants to improve the Greasemonkey support, for example by confining particular Greasemonkey scripts to particular Web pages and letting the browser update its scripts as it's running.