Challenges of any software project include: build vs integrate, and how to keep all the dependencies in sync.
One specific WikiSuite component criteria is to be "Multi-functional" / "All-in-one" to avoid complexity and plugin problems. Another specific strategy is to work closely with all components and improve the code upstream.
Here are some notes about each component.
Every 3rd release is LTS for 5 years.
Most cost-efficient process is to develop in trunk, in time for April and October releases.
Backporting is possible
No fixed time frames for releases, but cadence is fast enough.
Openfire Meetings bundles several apps (Jitsi Meet is the big one), and it's a challenge to keep everything in sync.
As a GNU/Linux operating system, there is a lot of flexibility in getting packages, but it's a slippery slope to dependency hell.
Upstream has a release every few years, and a very long support cycle. Tends to package older versions, which forces us to do things like: How to install PHP 5.6 on ClearOS
Kolab has a lot of moving parts, including Roundcube
Yearly releases, with LTS for 5 years
There are major upcoming changes with the move to the JMAP protocol. See also What is JMAP replacing?
https://kolabsys.com/installation-guide/overview.html
https://kanarip.wordpress.com/2015/12/04/the-evolution-of-kolab-development/
https://kanarip.wordpress.com/2016/02/02/introducing-winterfell/
https://docs.kolab.org/developer-guide/index.html
https://github.com/cyrusimap/cyrus-imapd/blob/master/docsrc/imap/developer/jmap.rst (Kolab uses Cyrus by default)
Syncthing follows a rapid release process. As a p2p app, if the protocol changes, old versions can't sync data with new versions. It is possible to set your Syncthing to get always the latest releases, or to have a slight delay.