How do I modify file/folder permissions?

You can modify the permissions of files over SFTP and FTP using ExpanDrive, you just can’t do it in the Finder. If you open a Terminal and use the 'chmod' command to change permissions, you’ll find that it works as expected.

Many users would like to be able to adjust permissions using the GUI interface in the Finder’s “Get Info” panel, and we’d really like to make this work. Unfortunately, starting with 10.5 the Finder stopped using simple system calls (which ExpanDrive supports perfectly), and instead adjusts permissions using an undocumented extended attribute of the file, and we can’t quite figure out what we need to do make this work with ExpanDrive. We’re still looking into it, and if we can’t make anything work then we’ll probably implement a system like we use for S3.