Not sure if there is one 'right' answer to this question...
The 3D probing plugin which is a free download generates a kind of Gcode directly from the scan but, this might not be the 'ideal tool path as it is really just a point cloud with X,Y & Z coords. IF you edit the file and add commands Like M3, G01, F, etc you might get a cut that looks representative.
Rhino 4 (a free download) will readt .txt point cloud files and then you need to mesh and surface the cloud and save it in a format that can be generated into G-Code. Rhino will only let you do 25 Meshes, then you have to buy.
Meshcam will generate G-Code from surfaced cloud files. Ger21 wrote a macro for Autocad that reads point clouds so you can save as.dxf which Lazycam could theoretically generate the Code for but, I never could get his macro working, maybe you might have more luck?
HTH,
Sid