Identical config files aside, the concept itself is rather simple and it has been around for ages in a form of ASN.1 and its encodings. It also routinely used in custom network protocols, e.g. IPC or RPC ones. Anyone outside of the XML fanboy club is aware of these things :-)

File format wise, it's hardly a rocket science too. When developers re-implement something, it's only natural to recycle an established implementation element. Changing it just for the sake of being different from another vendor is frankly quite dumb.

So I'd be careful with bold "rip-off" statements. In the end "Everything new is a well-forgotten old".