Yes you can move your project files between various computers and you can merge projects. So for example, if you had a team project, you could have several coders working simultaneously in remote locations and share the files through a system like Dropbox. The remote project files could then be merged so everyone can see everyone else's coding, annotations, analytical memos and any other pertinent information. One caveat though. NVivo is not backward compatible. So if you were working using version 8, I could open your project in version 9 but not the other way around. If you all use the same version then there is no problem.
Hope this helps!