Hi there
If you're intending to rank both pages, then you will need to create unique content for both of them. Replicating or syndicating the content would severely hamper your ability to rank either of the pages.
If you want to include the content for the user but do not necessarily want to rank the page, you have a couple of options. You could a rel canonical tag to the new page that points to the old domain - this effectively tells Google to treat the old URL as the original and not to rank the duplicate content.
Alternatively, you could "noindex" one of the pages by adding this tag to the head section of your HTML: _-_again, this tells Google not to index this version of the page with the duplicate content.
You can learn more about canonicals and noindexing with these two handy SEOMoz guides:
http://www.seomoz.org/learn-seo/canonicalization
http://www.seomoz.org/blog/duplicate-content-block-redirect-or-canonical
Hope this helps.