Correct, unless WordPress goes AGPL then Wix can keep their hosted code to themselves. However, the Android App which they should of made themselves will need to be open sourced or taken down and open sourced. The GPL if I remember correctly makes it so upon request (thinking of BMW) you must be able to provide access to the source code, even if you sell the product, that means that whoever buys a GPL'd product from you must also receive the code, but if they didn't buy your product there should be no reason for them to have it if I'm not mistaken. The GPL is interesting, and while not my first choice, it's definitely not a terrible choice.
