Not necessarily. Occam's Razor. It's more likely that they used something obscure to compile or obfuscate the code or wrote a tool to do so. Creating a new language just to write this seems highly unlikely.
Is writing something like this in pure assembly beyond the realm of possibility for some reason? There are still a few dedicated people that code on the metal for high level operating systems (Steve Gibson comes to mind immediately)
Writing something like this in assembly isn't impossible (or that difficult), but the patterns look like something that you wouldn't be using if you were writing in assembly.
My bet is that it's just C with a hand-rolled OO framework.
