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Cloaking can be used to keep people from using the content you display to search engine spiders, but it can do nothing to protect the content you display to everybody else.
If someone is using a frameset to grab your web pages directly, then you could implement some mod_rewrite code to keep them from doing so, but they could still access your site in a browser and simply copy and paste to steal it.
You might be better off sending them a cease and desist notice, and if that fails, sue them.