Due to financial and usage considerations the reference works licensed from Columbia University Press and Houghton Mifflin Harcourt have been removed as of June 2009.
The consolation is that you can look up the notes indexes from the Internet Archive:
and then look those words up at dictionary.com whose results include the full American Heritage entries, including the notes.
There doesn't seem to be a way to get to the Indo-European roots appendix.
Wonder how obnoxious it would be to actually buy the electronic AHD.