Yes,
You can do upto 6 axis machining, BUT here is the caviot. Mine is set up like a Trunion table type like a 3+2. If you want to do "Continous 5 Axis" then you would need to have a CAM program that could post it all out. Mach itself does NOT (currently) do Axis Translations (like if you have 4/5 on your Spindle). There are no G Codes for doing Axis Translations (Kinimatics). So all of that load would fall on your CAM package.
I use OneCNCXR2 Mill that has a "Positional or Continous 4th" and a Positional only 5th.
Scott
Commercial Mach3: Screens, Wizards, Plugins, Brains,PLCs, Macros, ATC's, machine design/build, retrofit, EMC2, Prototyping. http://sites.google.com/site/volunteerfablab/