I have an application that uses WinSCP (command line calls to WinSCP.com). It should be fine, within the license, to say WinSCP is a dependency and that the users must download and install WinSCP themselves. It would however be more convenient to just bundle the portable version in the installer of my application (should be easy to download and install WinSCP, but some users are less technical and they might have Windows XP in which case they have to download the portable version and manually extract and place somewhere my application will find it). It's however not straight forward to decipher whether this is permitted or not for GPLv3. People even debate whether it is or not, the debate being "is it a derivative work or not?". In my mind I'm not making anything close to a derivative work, just using it to synchronize to/from FTP server. I know this question really pertains to GPLv3 rather than WinSCP itself, but what is your take on this?