The popular interpretation of responsive web design has been, I feel bastardised. It's not just about a fluid grid with break points in your CSS to move things around depending on the size of your viewport.
It should be much more about how system responds to where, how and why it's being used. That might well mean apapting the layout to fit a smaller device, but equally it could mean things like presenting considered controls to touch devices, offering geo-aware information, changing content to user patterns etc.
The term itself is derived from responsive architecture which is defined thus:
Responsive architectures are those that measure actual environmental conditions (via sensors) to enable buildings to adapt their form, shape, color or character responsivelyhttp://en.wikipedia.org/wiki/Responsive_architecture
Go Cardless have made the right decision for them about layout, but I can't help feeling that they're setting the conversation about RWD back.
I think Potato make a lot of use of it. They've got some tools in their GitHub https://github.com/potatolondon and some really interesting projects in their portfolio http://p.ota.to/work/ (no surprise with Google among their clients.) They do a lot of Django work.
They don't, though.