I guess you are trying to use the only jar-file available in that directory to start the server?
Problem is, that file is not a complete minecraft server. That is the file that contains a lot of modifications and routines for running mods on a minecraft server.
You need to log in to your server with ssh, go to the server directory, and run “FTBinstall.sh” to actually get and compile a server version you can run. This produces a server file you can run.
I reccomend reading through this thread for a discussion and howtos for installing a FTB server, and some of the pitfalls, and commonly met bugs.