A lot of the posting goes on in a private section of my forum, and I'd like to duplicate some of the threads from the private section and post them in a public section.

I do not want to move threads because then they wouldn't be available in the private section

I do not want to split threads either

Is there any way to do this?

The only way would be to re-post them in the area you want them to be in. Do you mean threads/messages/posts or topics?

Threads. 

And I wouldn't want to repost them either, as the author of the thread wouldn't be credited.

I suppose I could ask users to repost them, but it'd be good if admins could configure one thread it be in two forums.