Yes, it is, although it's primarily a US journalistic convention. "Lede" is a publishing industry word referring to the most important leading detail of a story. It's spelled intentionally "incorrectly" to disambiguate it from the metal lead, which was used in typesetting at the time.

No, it isn't. It's an American thing at most and possibly also a false etymology. Its prime usage appears to be for people in HN threads to pat each other on the back for knowing it's "real" spelling.