In Windows the Dropbox client uses python25.dll and the MS C runtime libraries (msvcp71.dll, etc). On OS X the Python code is compiled bytecode (pyc). My guess is they are using a common library they have written then just have to use different hooks for the different platforms. What method of development is this? It clearly isn't IronPython or PyObjC. This paradigm is so appealing to me, but my CS foo and Google foo are failing me.