I've run Edition 5, Liquid 6, and Liquid 7 all on the same system at the same time, but it's absolutely not recommended. You have to install everything in it's own directory tree, and bear in mind that there's a shared Pinnacle directory as well (this is what trips people up when they install Studio and Liquid on the same system at the same time). Please note that I've never tried it with the Silver board set, Intime boards, etc.
Back up your system before trying this!!