This is simply a modification of the Google Butler script without the 'Enhanced by Butler' tag at the top. It was driving me crazy seeing it there, and I figure if you've gone through all the trouble of finding and installing Butler, chances are you probablly know what it is.

"What does Butler do? It links to competitors from the Google search result, removes ads on most Google pages (including Google Answers), fixes fonts, and adds links to other movie, product or weather sites. In Google Print, it removes image copying restrictions and adds links to other book sites. Future versions are planned to also remove ads in Gmail, as the Butler source code reveals in its comments."