He's advertising their cloud development platform. If it was AWS, not much different, as the Kindle Fire's a direct competitor to Apple.

Years ago, when the MS hatred was a bit more intense on places like Slashdot, I amused myself with capturing screenshots of Microsoft ads on their site. Here's a few from my old blog:

http://web.archive.org/web/20020929185648/http://www.mr-bill...

(Today that's no big deal since ads are served based on your browsing history if you don't block, but in 2002, I think that was less likely)