The official repository is a Darcs one. Here's a github clone.
UCW documentation is available in the source repo.
The documentation page on the UCW website has some background material.
[2020-28-01] UCW demo with Bootstrap 4: https://www.huuii.com/people/juan/5403 It was announced by his maintainer on Twitter.
[2009-09-19] Blog post on preparing for UCW development
[2007-11-24] Blog post on trying out UCW
There's a similar and more recent effort called WUI: dwim.hu.
A very brief assessment of all web frameworks listed in cliki was carried out in September 2010. This assessment comprised: check websites, download source if available, attempt to compile, review documentation.
The review found that UncommonWeb was well established. However, much of the documentation was stated to be out of date, which is off-putting but at least implies an evolving system. Some copyright dates as recent as 2009 indicate that it is still being developed.
There were no obvious links to example live applications built with this kit.