Yahoo!’s Zimbra subsidiary, which makes open-source messaging and collaboration software, today announced an upgrade for its Apple iPhone client software.

Zimbra Mobile for iPhone 2.0 talks to the Zimbra Collaboration Suite to enable features such as over-the-air synchronization of calendars, address books, messages and pictures.

Although the company’s open-source server is cost-free, there is also a commercially supported version.  A test version of the mobile software is also cost-free, while annual licenses starts at $500.