The change has noting to do with the viewer. It was designed to display protein data from a file called a .xyz format which was produced by some versions of gromacs. Later versions of gromacs decided not to produce that format so the well-tested versions of the viewer stopped working ... gradually ... as more an more projects began doing better science using the newer versions of Gromacs while projects that still produced the .xyz files still worked.
The viewer developed for V7 works fine with any FahCore that still produces a .xyz file but for most people, it just displays the test protein. There's an open ticket to teach the viewer how to read .trr and .tpr files (see
#409) but it requires data from both files and Gromacs produces more than one format of those files so it's a significant enhancement to make the viewer work again.
It turns out to be a rather complicated problem, especially since so many people choose NOT to run the viewer because it uses resources that could otherwise be used to do more science and earn higher PPD. (Personally, even if the viewer were 100% problem free, I'd still run it rather rarely but that doesn't mean it's not important to others.)
Oh, and the viewer also comes in more than one flavor, depending on which version of graphics support it's talking to. Programming resources are, in fact, limited, and for all of these reasons, it gets assigned a lower priority than quite a number of things that limit what can be done with the folding calculations, themselves.