The source code is available from http://ftp.gnu.org/gnu/solfege. If you are adventurous, you can try the unstable (buggy, but might contain new stuff) releases from http://alpha.gnu.org/gnu/solfege. These releases might have more bugs, but then you get the chance to try new stuff and find and report bugs.
Source code and some precompiled binaries are available from http://sourceforge.net/project/showfiles.php?group_id=1465.
If you run Debian you can
apt-get install solfege to download and install the program.
If you want to report problems installing or running Solfege, or have questions, comments or ideas on how to improve Solfege, please post to this list instead of using the message forum at Sourceforge or the author directly. You can post to solfege-devel without subscribing. (Subscription | Archive)