The Encyclopaedia Britanica is to launch a subscription service on ios according to digitalspy. The app will cost around £1.99 or around 2.50 dollars per month.
If subscribers do not pay for the app, there is a free one available, but this free app will only offer a limited amount of data.
There is no doubt it will probably be ported to Android within a few months after it gets released on ios, because Android has a large user base.