gFTP is stored in GNOME's SVN repository. For instructions on how to setup your subversion client, visit the website http://developer.gnome.org/tools/svn.html. In a nutshell, you will need to run the following command to download the latest code:
svn co http://svn.gnome.org/svn/gftp/trunk gftp
To compile the SVN code, you will need autoconf, automake and gettext installed on your system. Once you have those packages installed, run the following series of commands:
Run ./autogen.sh to generate the configure scripts.
If that is successful, run ./configure to generate the Makefiles. By default, the binaries will be installed in /usr/local/bin. You can change the install location by passing the --prefix argument to configure. For example, let's say you want to install the binaries in /usr/bin. Run configure --prefix=/usr.
If that is successful, run make to build the source.
Optional: If that is successful, run make install to install the binary on your computer.