The .midnam and .middev files were not created by MOTU, nor borrowed from them. The XML specs are part of a general 'interop' development movement that includes other programming languages like Java, HTML, XHTML and SGML. The language itself is still developing, which is why you can see slightly different 'standards' being used and why there can be compatibility issues. As with anything in it's infancy, some parts are still trial and error.
You can find more info on XML here:
Extensible Markup Language (XML) at the Society for Scholarly Publishing