The law was enacted in 2009 to replace blasphemy laws enacted by the pre-independence British state, dating back to 1703, pending a constitutional referendum to have it removed completely. This came about on the back of a paper produced by the law reform commission 1991, so there was quite a bit of foot-dragging. (It was not, as the article implies, newly invented in 2009).
The complaint against Stephen Fry, as mcphage alluded to here, was made not by an offended conservative Christian, but rather somebody attempting to make a point about the now over 8 year delay on holding the referendum to remove the law.
Unrelated aside: the article also says Fry was joking about his belief that a hypothetical Christian god would be “quite clearly a maniac.” I don't believe he was.