No, Articles and other content items cannot be assigned to multiple categories or sections. In Joomla! 1.0 and 1.5, content items are restricted to a single category in a single section.
Possible work-arounds include:
- creating duplicate articles in multiple categories.
- using menus rather than dynamic lists of content items.
- using various third party extensions that simulate assignment to multiple categories.
- using key words to simulate categories and sections.