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.