Craigslist is suing apartment-searching web app PadMapper and its data provider, 3Taps, over allegations of copyright infringement, breach of contract, and several other charges. The suit comes after the company's cease-and-desist letters were dismissed by PadMapper founder Eric DeMenthon earlier this month.

3Taps provides an API for web developers — like those at PadMapper — to easily access Craigslist's listing data. While PadMapper does use this data to locate apartments, when a user clicks a listing the corresponding Craigslist page is opened in a frame. In a blog post from earlier this month, DeMenthon argues that because PadMapper "doesn't touch [Craigslist's] servers," it isn't subject to the site's Terms of Use (TOU).

Craigslist cites its TOU in its lawsuit, which say:

If you access craigslist or copy, display, distribute, perform or create derivative works from craigslist webpages or other CL intellectual property in violation of the TOU or for purposes inconsistent with the TOU, your access, copying, display, distribution, performance or derivative work is unauthorized.

The TOU also states that caches of Craigslist's data count as copies, and the company's lawsuit claims that 3Taps is doing exactly that when it copies data to its private servers. We'll have to wait and see how the courts decide to handle the suit, but in the meantime neither PadMapper nor 3Taps have decided to remove access to Craigslist's data through their services.