1) Padmapper and 3taps are using Craiglist's site; they are simply used a copy of the site. That difference is not relevant from a legal standpoint given their specific use.
2) It's basic contract and copyright law that a licensee may defend a copyright if necessary to protect their license. See Righthaven, which came down to this very issue: Righthaven was prevented from asserting newspapers' copyrights because it did not have a license to the newspapers' content.
3) You have this backwards. Padmapper and 3taps are (a) the ones breaching the contracts between themselves and Craigslist (see 1) and (b) are interfering in the license agreements between Craiglist and the posters. The posters are not breaching anything.
1) The difference is not relevant in respect to copyright law. The difference is very relevant in respect to my layman's understanding of contract law. How can Padmapper or 3taps enter a contract with Craigslist without interacting with them at all? Am I bound by Craigslist's terms of use if someone hands me a printout of a listing?
2) From the Righthaven opinion[1]:
Pursuant to Section 501(b) of the 1976 Copyright Act, 17 U.S.C. § 101, et. seq., (the “Act”) only the legal or beneficial owner of an exclusive right under copyright law is entitled, or has standing, to sue for infringement.
Righthaven owned the copyright to the work in question, but granted all of the exclusive rights back to the original creator. While Craigslist has a license to its listings, its standing to sue for infringement doesn't seem clear to me. I'd love to see a counterexample.
3a) Presumably, 3taps and Padmapper no longer access Craigslist. As a result, they are no longer bound by their terms of use. From the TOU: "If you do not accept and agree to all provisions of the TOU, now or in the future, you may reject the TOU by immediately terminating all access and use of craigslist, in which case any continuing access or use of craigslist is unauthorized."
3b) I see no interference in the license agreement between Craigslist and the posters. Craigslist's license is non-exclusive. Padmapper's use of the posters' content does not breach the license agreement.
Call me an armchair lawyer all you want, but so far, your arguments seem to contradict the facts.
1a) Exactly.
1b) They are still using Craiglist's site by interacting with the cached copied of Craiglist's site. I don't know how clearer I can make that. The only way they would not be using the Craiglist site is if they used another listing service altogether.
2) Legally, Righthaven did not own* the rights in question, and that is why the Colorado court kicked out their lawsuits. The court concluded that Righthaven merely owned the right to enforce the copyright because it had granted all the actual exploitation rights back to the newspapers. In other words, Righthaven's "ownership" was illusory and intended solely for the purpose of given them standing to sue. Unfortunately (and I do not know how Righthaven missed this), it has been longstanding doctrine in IP Law that a transfer of all exclusive rights to an IP constitutes an actual transfer of the ownership of the IP (litigation rights are not considered rights in this context).
3b) They are accessing the cached copy. They admit as much. A duplicate is the same as the original, for copyright purposes.
3b) Posters license Craiglist to use their content. They do not license anyone else to use their content. Padmapper is thus an unlicensed user. This can constitute tortious interference in many states because it interferes with Craiglist's ability to full exploit their license.
If Padmapper was using a competitor of Craiglist that the poster had also posted to, there would not be any problems. But Padmapper is using Craiglist's own service, and that factual distinction matters.
4) I don't know how to say this more clearly: you are misunderstanding the legal holding of the Righthaven opinion and how the IP law works in the U.S. It is probably an honest mistake, since IP law adopts a lot of physical property concepts that most techies instinctively reject.
2) It's basic contract and copyright law that a licensee may defend a copyright if necessary to protect their license. See Righthaven, which came down to this very issue: Righthaven was prevented from asserting newspapers' copyrights because it did not have a license to the newspapers' content.
3) You have this backwards. Padmapper and 3taps are (a) the ones breaching the contracts between themselves and Craigslist (see 1) and (b) are interfering in the license agreements between Craiglist and the posters. The posters are not breaching anything.
Don't be an armchair lawyer.