[geoffschmidt]

There are a variety of theories of copyright infringement in the US: direct infringement, contributory infringement, vicarious infringement, and inducement to infringe. I don't remember exactly which would apply to the circumstance you're describing, but in general, if you're making money off of someone else's infringing activity, if you are tolerating infringement that you have ability to stop, or if you have a landing page that suggests that people use your product to infringe copyright, you're probably in hot water, even if you're not infringing copyright yourself.