College Board's Course Authorization letter for Khan Academy AP courses

As homeschoolers, my family has been using Khan Academy courses for the last 6 or more years. We are very grateful for such a wonderful (and free) resource!

This year, I am using Khan Academy's AP/College Physics 1 course for a high school senior. Our transcript service requires a copy of the Course Authorization letter (or form) sent to Khan Academy by the College Board to accept a course as AP level for high school transcripts. Where would I find a written, printable authorization letter or form that shows that College Board has approved Khan Academy's courses as AP level? I tried searching for "AP authorization," "AP Letter," and "College Board" within the Khan Academy Help Center, but none of the entries on the first 3 pages of each seemed to be what I need. 

I did notice the footnote at the bottom of the AP/College Physics 1 course welcome page that states "AP® is a registered trademark of the College Board, which has not reviewed this resource." Are the Khan Academy AP courses not confirmed by College Board at all? Are curricula companies allowed to use "AP" in descriptions if their coursework has not been reviewed by the College Board?

Thank you for your help.