The already mentioned XML based CCMS "Calenco XML CMS" still available (see also my post "Open Source CCMS").
There is one more system which lately offers an already existing DITA based CCMS without any license cost: "SiberSafe DITA CMS". Read the EULA carefully but in case you need something to play with....
Both are no more open source. Their goal is not to get an open and shared development. They simple heading for lowering the barrier for customer entry.
What you see is that both cases are the company driving the implementation want to get in tough with you and both companies offers additional features with dedicated license costs.
I personal expect more product in this domain following the same approach. Why?
The specific domain of "technical documentation" is pretty small and there are many different and small companies out there which providing specific products to support this domain.
Even in huge installations the amount of licenses required to support the users dealing with technical information isn't very huge - this means the opportunity to sell a huge amount of licenses is limited. In addition most of the available tools are similar to each other - with individual advantages but with no structural differences.
This means this business model does not really scale and the amount required to sale the license is high.
On the other hand having a tool does not improves your information process and therefore does not add any business value to your organization. At the best case it supports your process with automated tasks. But first of all you need a optimized methods and processes (information process) at all before any tool can assist you as best as possible.
This means - the future is not to create and develop products looks like the today's CCMS system available on the market. The future is to create either information process driven productions where technical information is just one use-case OR focus on integration services to get the value out of existing information.
What are the limitations of todays CCMS system. And how more future oriented designs will look like? More to come in future blog posts....