Is there a simple way to download an SVN repository that is exposed on the web using ViewVC?
There are 2 ways this question could be interpreted, but the short answer for both is no:
ViewVC is meant to be a repository viewer, so there is no option to download all the files in a section through the web browser. It might be possible to write a script to do this, but that would take a very long time I imagine, especially if taking into account folder structures.
If you mean that you want to download the actual dump of the repository, the answer would still be no because the repository folder would be stored either locally on the machine, or somewhere ViewVC could locate it. If you know where the file is, anyway, you could just use a repository browser (such as TortoiseSVN on Windows) to view it and download from said browser.