multiple listing of a site's pages-- is it abuse?

I don't know if this is abuse because I am not an expert on the guidelines, so is it allowed for a website to be listed under one category, but individual pages from the site listed in several other categories?

It depends. Normally we list only a sites main page but in some cases where the content of a site is varied and comprehensive other sections of the site may be listed in other parts of the directory. It is called deeplinking and it is discussed in our editorial guidelines here

http://dmoz.org/guidelines/site-specific.html#deeplinks

Hope this helps.