I'm afraid you're asking an unanswerable question, in the wrong place. If you had a clue what software (which is a mass noun) is most widely used for learning English, then you could focus of their "method". It might be that some obscure company has corner the Chinese-speaking market and is thereby the most "common". You also need to distinguish software as a supplemental tool for teachers, versus self-taught methods (e.g. Rosetta Stone, Pimsleur).