Using non-free software on a libre software computer aka one with a fully
free distro, is something some people probably do. If you have to though, I
recommend keeping that stuff as disconnected from the internet as possible.
That being said, I agree with thejames. although I understand some users will
break rule 2. I myself have on occasion, but yeah its better to not break
that rule.
As a rule of thumb, the default software on any free software laptop should
have nothing proprietary or freedom restricting. Emulators included, but the
files they run are another story entirely... some would say these matter, but
meh to each his own.
I would refer to my first post though if you seriously want a quick answer to
your question.
Long story short, if you have to, use non-free, better to have the rest of it
be freedom respecting to offset some security issues as much as possible.
But obviously not recommended. ;)