Tom,
Sure you need an API for webDAV. That is true. You can also create your own HTTP based access, that will also need to be programmed. If you create your own HTTP based access method you also need to write your own client software.
With webDAV there is a consistent interface between web content and authoring client software, or at least that is the goal. I think its still a work in progress.
Of course, noone is required to use a webDAV interface, and the existence of webDAV does not limit to using a more traditional HTTP access method.
There are already several HTTP based access methods for web site content, and it would also be nice to have that feature available for OpenACS developers and users.
I do think you are misunderstanding the goals of webDAV and who we are thinking about here. I am trying to make it easier for content editors who work in MS Word or whatever. These editors do not have shell access or CVS access to the web site. Even if I would grant them this access, they don't want to learn another tool.
For web site programmers, CVS is the best way to change how the web site works.
If these roles are combined, maybe webDAV is not the best way to go. It would just be one more option for those who choose it.