WhatsApp, the popular mobile messaging app that eschews advertising in favor of a paid model, is getting ready to bring its iOS app in line with the apps it makes for other platforms by turning it into an annual subscription service. Jan Koum, WhatsApp’s CEO, says that the company is planning this year to shift its iOS app to one where new users would pay annually to keep using, taking it away from a one-off download fee and bringing it in line with how it is distributed on the Android, BlackBerry, Nokia and Windows Phone platforms. The comments were made to Dutch journalist Alexander Klopping, and reproduced in part in two Dutch blogs, Tweakers and Techtastic. Klopping also provided us with recording of the interview, in English. The new subscription model would apply to new users, Koum said, and would likely follow the same pricing structure as its other apps.