From Zimbra :: Wiki

Note: Only Network Edition Customers may rebrand Zimbra. Open Source users may freely create themes.

Please consult the ZPL Zimbra Public License for more information: http://www.zimbra.com/license/zimbra_public_license_1.2.html

• ZCS 5.0x Theme Instructions

• About Creating ZCS Themes

• Changing the Page Title

• Using ZCS Theme Color Picker

• Theme Directory Structure

• Customizing Themes and Adding Zimbra Powered Logo - Open Source Edition

• Creating Themes Long Version