ClearOS was picked as the underlying operating system for WikiSuite.
CentOS is a general purpose operating system. On a fresh install, it does very little. You need to pick and choose amongst tens of thousands of applications to get the functionality you need. And there is very little if any functionality to make the various apps work together.
It is easy to convert a CentOS to ClearOS: How to upgrade a fresh install of CentOS to ClearOS
Although there are variations (Ubuntu Desktop vs Ubuntu Server vs Ubuntu Server for Cloud), Ubuntu is a general purpose operating system. On a fresh install, it does very little. You need to pick and choose amongst tens of thousands of applications to get the functionality you need. And there is very little if any functionality to make the various apps work together.
ISPConfig was the original server admin panel component for WikiSuite (It was still called Tiki Suite back then), as you can see in slides from 2011
But ClearOS was picked.
WikiSuite is about having all the tools for one organization, and available on premise or in a data center.
For an eventual offering of WikiSuite as SaaS, we will need a platform to manage multiple virtual machines, not a platform to manage shared hosting applications. See: Orchestrator.
We have been working with the ClearOS community to improve it as a hosting platform, and get some of the benefits of ISPconfig.
When is ISPConfig better? If you are a provider of shared hosting
Webmin doesn't do much to hide the complexity. It just gives you a
web interface and a little syntax checking but you still have to know
what programs you need to manage and what all the options mean to
modify any particular service. ClearOS/SME/NethServer management
interfaces are much more task/function oriented and you generally
manage them without needing to know much at all about the details of
the underlying programs. Some of the form actions may in fact affect
more than one program's settings.
On the good side, Zentyal is based on Ubuntu which has a nice and predictable release schedule.
Long after we started working with ClearOS, Zentyal chose to remove lots of functionality, including the web server.
In contrast, the WikiSuite project has lead to multiple enhancements to ClearOS as a web server (ex: Let's Encrypt, PHP version selection, better configs, better handling of multiple sites, etc.)