With the Four Thirds Standard being around for quite a bit longer than the MFT (Micro Four Thirds) there is an actual way to use those lenses on a MFT System such as the Panasonic GH2 or any other Micro Four Thirds Cameras using the Panasonic DMW-MA1 Four Thirds to MFT Adapter. Lenses, such as the Panasonic/Leica 14-50mm f/2.8-3.5 OIS Four Thirds Lens can be used on Micro Four Thirds Cameras - but the question remains, if there is an actual way to use four thirds lenses on Canon EF Systems, since the Panasonic/Leica Lens D Vario-Elmarit 14-50mm 2.8-3.5 ASPH is a very good Lens.
Unfortunately, the optics of 4/3 and MFT (Four Thirds and Micro Four Thirds) imply, that the image size projected on the sensor is smaller than any full frame or APS-C sensor so there would be a massive vignetting (a reduction of an image's brightness or saturation at the periphery compared to the image center), producing pictures as the ballon-picture on the left. A gradual decrease in light intensity towards the image periphery happens, so it actually does not make so much sense to use MFT or 4/3 lenses on systems with a larger sensor. Still it totally makes sense, to use lenses designed for 35mm or larger than four thirds on any FT/MFT system, such as the Redrock Micro LiveLens, Active Lens Mount for Canon EF Lenses. In another post, I will write a comparison on legacy lens systems and the usage on MFT/FT and EF systems.