Depends on what they mean by "licence key" in their terms, it would usually apply to an account with a licence but could also be literal.
After much looking around it would appear that Mojang have no problem with people selling accounts. Seems they only care about you selling the stuff to make accounts.
When you buy our Game, we give you permission to install the Game on your own personal computer and use and play it on that computer as set out in this EULA. This permission is personal to you, so you are not allowed to distribute the Game (or any part of it) to anyone else. This also means you cannot sell or rent the Game, or make it available for access to other people and you cannot pass on or resell any licence keys. You may however give gift codes that have been bought through our official gift code system. This is important to help us stop piracy and fraud and to protect our Game. It is also important to prevent members of our community from buying pirated versions of our Game or fraudulent licence keys – which we may cancel, such as in the case of fraud.