Short answer: Yes and No.
When re-writing a URL if the hostname changes it is necessary to send a redirect to the browser.
DreamHost will let you specify the document root ("Web Directory") of each site you host. So you can have more than one site hosted from the same directory, or even host sites from a subdirectory of another. And they also allow you to alias url directories to different file system directories using "Remap Sub-dir"
So by using a combination of mod_rewrite and changing the document root or using aliases you can re-write between sites in a more complicated matter than normal. What I mean by that is you would need to add a condition that checks the server hostname variable to determine which site is being accessed or adding an extra path part to the result.
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