John Gruber has a piece in MacWorld about AppleScript in which he says that Open Scripting Architecture was supported only by Apple. That's not correct.
AppleScript was not originally intended to be the only OSA scripting language, but it was. The idea was that OSA was language-agnostic, and the plan was for there to be several of them eventually. AppleScript was the friendly language, derived from HyperCard's HyperTalk (therein another story entirely) and intended for use by non-programmers. The theory being that a programming language that looked like prose rather than code might enable a broad swath of 'non-programmers' to, well, program.
UserLand's Frontier scripting environment supported OSA, both as a client and a server. The syntax of our language, known as UserTalk, is most like Python -- though it is a contemporary of Python, development started in 1988.