Nitrogen is correct, the fuzzyness in the US is around whether or not jailbreaking your own phone is a violation of the DMCA or not (ruled "no", then ruled "yes", not sure where it is at the moment), and then the contractual (civil vs non-civil) issues with running software on your phone without Apple's permission) It is that "grey" area, where folks can give themselves a credible story about how it is "perfectly legal" and so take the money. My point was that they are dealing with people who don't care if its legal or not. (remember they don't "charge" the end users, they charge the app store bundle guy). That guy (or gal) doesn't care about what is or is not legal, they care about money any way they can get it so that the person they got it from can't get it back. Period.
AIUI, jailbreaking (or any modification of software) creates a derivative work, which is a right protected by copyright. In other areas of copyright law, it seems commercial uses are more stringently restricted than personal uses.