English, like any other
language, is not
alive. This is merely a
metaphor. English, like any other language, is a set of
conventions.
It changes over time but so does everything else. Flowers bloom and metal rusts. Unlike physical artifacts, a social artifact such as English changes through the gradual interaction between how it is used and it was used. Sometimes this occurs through extensions and expansions of the vocabulary, the coining and dissemination of new words. Sometimes it occurs through deflation, the collapse of meanings so that words fall into disuse or the various meanings of a word become narrowed.
Interestingly, most arguments that use the metaphor of "English as a living language" seem to be concerned with justifying a narrowing and limitation of the language.