There is not yet a stable release of Unsyntax. You can, however, download the latest development version as a tarball.
After you have unpacked the tarball, you can do the usual
$ ./configure $ ./make $ ./sudo make install
Afterwards, you should be able to run the Unsyntax interpreter with the command
$ unsyntax-scheme [options] [--] [program [arg]...]
and the compiler with the command
$ compile-unsyntax [options] file
See the file INSTALL for generic compilation and installation instructions.
Unsyntax requires (the development version of) Chibi-Scheme to build and run.