I think it would be a great idea to be the "first" to provide sync with iPhone.
It would promote Zimbra even more if its available in the opensource version.
Especially since it uses the standard technology like IMAP, i don't think it would require anything custom (maybe).
A great way to get people to read about Zimbra. Any Apple product news sells like hot cakes in news websites. So Zimbra support would go well
