OK, since someone asked, I threw together a Linux build of Topicalla. It also includes a page where you can test entering ReoPath expressions for RDF files. It may take some time for the download to reach the mirrors.
Currently, you can view RSS and FOAF info as well as some other stuff. So far, there isn't much of the magic that makes this project so interesting, so as yet, you might not think it was ' blisteringly innovative'.
However, it does demonstrate using Reopath to create XUL, instead of using XUL templates. The idea is to eventually allow something like the following (currently the syntax is a bit wordier):
<listbox id="rssItems" flex="1" rp:repeatOn="sort(rss:items[dc:creator='Neil'],dc:date)"> <listitem label="?rss:title"/> </listbox>
Anyway, if someone wishes, I will write some documentation about the interfaces used.