Hi Jim.
Duplicate content refers to the content itself being made available on multiple URLs. You can duplicate content internally or externally.
Would I be penalized for duplicate content if I purchased country-specific domains and pointed them to the .com site?
No. Let's assume you own www.mysite.com and also own www.mysite.fr. If you use a 301 redirect to point the french URL to your main site, there would be no penalty as all the content is still only on one site.
Another note is translated content is not considered as duplicate content.
A final note is country-specific sites can duplicate your .com site without it being considered duplicate content. If you have a .fr site it could be an exact duplicate of your .com site but the .fr site, assuming it was properly set up, would rank well in Google.fr whereas the .com site would rank well in Google.com or whichever country was the focus of the .com site.