The code you refer to is extremely old and only kept in the download for backward compatibility with old demos. There will definitely not be any further development on it as we now have our own TCP/IP stack FreeRTOS Plus TCP - A free thread aware TCP/IP stack for FreeRTOS
Will FreeTCPIP satisfy my througput requirement?
That will, of course, depend on your throughput requirements, which at this point only you know.