You are welcome to use, modify, and redistribute Zimbra Collaboration Suite (ZCS) Open Source Edition free of charge, provided you do so according to the terms of the appropriate License.
We welcome all ZCS users to join the Zimbra Community, and invite you to share contributions of bug-fixes, enhancements, or other modifications with Zimbra for consideration for inclusion in Zimbra. A good first step is join the Zimbra Forums and learn more about becoming a Zimbra Contributor.
For more information about licenses please review the License FAQ.
ZCS Network Edition is Zimbra's commercial software and service subscription; it includes support and optional training. It is available under the following licenses:
Both Zimbra Collaboration Server Open Source Edition and Network Edition bundle best-of-breed open source technologies. They are licensed to you when you use the ZCS binary releases under the same terms that they are normally shared with the world. For the detailed list of 3rd party open source licenses, see the 3rd Party Open source Licenses link on the downloads page for the applicable software version.
Older versions of Open Source Edition (before ZCS 6.0.5 and ZCS 5.0.22 and after ZCS 5.0) are governed by the original license grant that Yahoo!, Inc. made on the date of that software’s release (all such dates being prior to February, 1 2010). The source code is under the Yahoo! Public License (YPL) and binaries under Zimbra Public End-user License Agreement (EULA).
Older versions of Open Source Edition (before ZCS 4.5.8 as well as releases of ZCS 5.0 prior to ZCS 5.0 Release Candidate 1—5.1rc1) can still be found on Sourceforge.net. These prior versions of ZCS continue to be governed by the original license grant that Zimbra, Inc. made on the date of that software’s release (all such dates being prior to October 4, 2007): the ZCS server is under Mozilla Public License (MPL), and the ZCS Web end-user and administrative clients are under Zimbra Public License (ZPL).