I was unaware that copyright in the UK was so extreme. That's unfortunate.

The topic at hand, however, is a DMCA action between two US entities (the RIAA and GitHub) and so is purely a matter of US law AFAIK. My understanding (possibly mistaken) was that the courts here had nearly always permitted making personal copies of otherwise legitimately obtained media. In fact, my understanding is that reversing this status quo was one of the primary motivations behind the DMCA; by disallowing circumvention of protection schemes, in many instances it effectively outlawed the tools needed to make otherwise permitted copies.