"Wiring", which constitutes Arduino's primary API surface, was taken wholesale from Hernando Barragán's 2003 master's thesis project. It was a fork of processing for microcontrollers and was not written by the Arduino team: Massimo Banzi, David Cuartielles, David Mellis, Gianluca Martino, and Tom Igo.
Yeah, the software side is basically only an IDE, a build system and a package manager an another system API (basically an alternative to libc). Which is useful for C++, but far from being non-replaceable.
