I think it really depends on what purpose the ‘Rainbow Tables’ served. You might run into problems if the primary purpose of the tables was to disguise the distribution of files where the copyright was questionable.
Normally, you can host just about any content on DreamHost, just as long as that content is legal in the United States. I am no lawyer, but it seems to me that certain uses of ‘Rainbow Tables’ may fall foul of the DMCA or similar legislation.
Edit: As with other questions along these lines, I think your best option would be to contact DreamHost (via the contact form linked below) outlining exactly what you intend to host and obtaining an authoritive answer from them as to whether it would be allowed under their TOS.
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