From what I understand you still need Xcode to sign the package with your developer key to either load it onto a device to test or to send it off to the app store. Though that might not be the case anymore as I haven't looked in a long time.
Had anyone ever tried to challenge this in a court?
Some jurisdictions have customer protection laws that say it's illegal to require purchase of some goods (or services) as a condition for purchase of other goods (or services). Don't know English legal terms for this, sorry.