Several of the regulations are designed to protect Microsoft's interests: apps that alter the default browser, search client or media player on the phone are banned, as are those that encourage people to use a marketplace other than Microsoft's own.
http://www.alphr.com/news/252463/microsoft-reveals-list-of-banned-mobil…
Firefox: http://www.cnet.com/news/microsoft-bans-firefox-on-arm-based-windows-mo…