Hi,
These jobs are run by the batch daemon which indeed runs as the user 'kaltura'. So, for local dropfolders, the directory must be readable by the kaltura user. In UNIX, in order to list a directory contents or access the files under it, an exec permission is also needed, of course.
When using remote dropfolders and accessing them over SFTP, you provide the username and passwd to access with, naturally this user needs to be one with permissions to retrieve the file from the server.