Yes, it's no problem using several versions of FrameMaker on the same computer. I've had versions 8, 9, 10 and 2015 sitting on the same PC without any issues, however, these are the common caveats:
If you've got a full version of Acrobat Pro installed, do not install the PDF printer instance coming with FrameMaker
When uninstalling a version of FrameMaker later, it's possible that the uninstaller messes up the registry. I've just had this happen when uninstalling FM9, my 2015 version wouldn't launch due to missing registry entries. This can be fixed, though, my 2015 version is running again.
The other gotcha with multiple versions installed is Windows knowing what application to launch if you open a .fm or .book file directly. Generally, it will be whatever version was installed last, but this can get screwed up.