Re: Topics vs. Categories
There's some overlap in their use, but I think "horribly redundant" may be a bit excessive. 
Anyway, better an overlap than a gap. 
Article topics were fashioned on the model of slashdot.org, I imagine, and are meant to be a rather simple article-specific way for readers to find or identify the news items. Typically at news sites, each article topic has a graphic icon to emphasize the identity. For users familiar with news sites that use this kind of visual identifier, the meaning is immediately clear (a "Linux" news item, a "Microsoft" item, etc.).
Categories are more complex since they can be in a hierarchy (but there's no method to assign an icon to a category and have it displayed). Categories in Tiki are "cross-feature" in the sense that you can categorize images or galleries, forums, wiki pages, news items and so on, mixing and matching the objects.
Probably if Tiki were being rewritten from scratch, it'd make sense to consolidate these things (same is true for the link directory "category" that has no connection to the feature "Category"). Or maybe some ambitious revamps of the articles and directory features will manage this someday.
-- Gary
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