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eGroupware   (Compare Project)

Very High Activity

Mostly written in PHP

License: GPL-2.0+

syncphony   (Compare Project)

Very Low Activity

Mostly written in Java

License: AGPL 3.0+

OBM   (Compare Project)

Very High Activity

Mostly written in PHP

License: AGPL 3.0+

OpenGroupware.org   (Compare Project)

Very Low Activity

Mostly written in Objective-C

License: LGPL

OpenGroupware Coils   (Compare Project)

High Activity

Mostly written in Python

License: MIT

Kolab Groupware Solution   (Compare Project)

Very High Activity

Mostly written in PHP

License: Unknown

Zarafa Collaboration Platform   (Compare Project)

Activity Not Available

License: AGPL

DAViCal CalDAV & CardDAV Server   (Compare Project)

Very Low Activity

Mostly written in PHP

License: GPLv3

Calendar and Contacts Server   (Compare Project)

High Activity

Mostly written in Python

License: Apache-2.0

Tine 2.0   (Compare Project)

Activity Not Available

Mostly written in PHP

License: AGPL

Funambol Mobile Cloud Sync   (Compare Project)

Activity Not Available

Mostly written in Java

License: AGPL-3.0

OpenLDAP   (Compare Project)

High Activity

Mostly written in C

License: OLDAP-2.8

Postfix   (Compare Project)

Activity Not Available

License: IBM Public License

Dovecot   (Compare Project)

Very High Activity

Mostly written in C

License: BSD-3-Clause, LGPL-2.1, MIT

ejabberd   (Compare Project)

Moderate Activity

Mostly written in Erlang

License: GPL-2.0+

CentOS   (Compare Project)

Activity Not Available

License: Unknown

Clam AntiVirus   (Compare Project)

Moderate Activity

Mostly written in C++

License: GPL-2.0+

RPM   (Compare Project)

High Activity

Mostly written in C

License: GPL-2.0+, LGPL-2.1+

Roundcube Webmail   (Compare Project)

High Activity

Mostly written in PHP

License: GPL-2.0+

SpamAssassin   (Compare Project)

High Activity

Mostly written in Perl

License: i9