Too: proprietary solutions cannot (at a sustainable price point) compete with the quality of free.
As someone noted -- there's a development model which shares the load among many eyes, and produces higher quality work as a result.
There are a few other mechanisms at work, but the upshot is that for utility, and even a fair amount of specialized software, there's no longer a marketplace for the software itself.
>Too: proprietary solutions cannot (at a sustainable price point) compete with the quality of free.
That depends entirely on the community behind the free solution, and what class of software it is. For instnance, I'm not aware of a FOS document management system which would compete with, say, Paperport or DevonThink (Windows and Mac systems, very proprietary).
I didn't say in all cases. Specialized, very high-value, and vertical tools particularly.
But generally the trend is that, starting with OS, development and management tools, and commodity software, Free Software is taking the financial value out of software sales.
For your example, OpenKM and LogicalDoc turn up for searches on "document management open source", though I couldn't say how they compete on functionality, scale, ease-of-use, stability, and/or management.
To shift spaces slightly: there's a pretty small market for proprietary Wiki software. Atlassian and Microsoft Sharepoint would be two that I'm aware of, though alternatives, especially MediaWiki, are very widely used (internal to the CIA even).
What's becoming more common is a service model based on free wiki software. Jimmy Wales has a startup based on offering MediaWiki pages, there's a similar offering based on TWiki that I'm aware of. I'm sure there are others. Similarly, blogging engines as-a-service. The software's free, but the service offering drives revenue.
Could be a way into the docs management market as well.
As someone noted -- there's a development model which shares the load among many eyes, and produces higher quality work as a result.
There are a few other mechanisms at work, but the upshot is that for utility, and even a fair amount of specialized software, there's no longer a marketplace for the software itself.