How can I publish an app on a fan page?
Obviously you need to have admin rights on the destination page, then you can use this url:
Substitute APP_ID with your app id (get it from the settings page on https://developers.facebook.com/apps) and insert the “Secure canvas url” (find it on the same settings page).
Then, if everything’s ok, you will be prompted with a list of pages; choose one and you’re done.
New Fan page look (“Timeline”)
After the switch to the new fanpages look and feel, I noticed that there is a limit on the number of apps that you can “pin” in the apps thumbnails list. The limit is 12 (three rows of 4 apps).
This is not a limit to the number of apps that a fan page can host; only a limit to the thumbnails list.