Which Dave? David Banks?
Yes, David Banks!
Thought so. He's the person who disassembled that version – I think, before the official source for an earlier version of BASIC IV was released on Github.
He's also the author of the two superb BBC cores (Model B and Master 128, both with second processors etc.) for the Spectrum Next. I tried very hard to get him to port these cores to the MEGA65, but was unable to persuade him, sadly. I really wish he'd do it; the MEGA65 would be a much better machine to run these BBC cores because it has a bigger and better keyboard than the Spectrum Next; it'd be far more usable with a lot of BBC software. (Plus, the presence of the 3.5" floppy drive would mean the MEGA65 would be a superb machine for running a prospective Master Compact core. There's no such thing yet, but it shouldn't be hard to adapt from the Master 128 core, and the MEGA65 would be ideal for using it.)
And he's also responsible for many other modern BBC projects, including PiTube Direct (use a Raspberry Pi to emulate virtually all the various BBC Tube second processors in a BBC model B or Master), MMFS (the SD card filing system) and many other things. He's an amazing chap. Today's 8-bit BBC platform wouldn't be half as interesting as it is if it weren't for him and all the clever extensions he's devised, both in software and hardware.