There is no release yet of Aurelia.
However it can be downloaded as a source tarball from the nightly tarball repository.
The second option is to use the svn repository https://svn.aurelia.cx/svnroot/aurelia/trunk . You will need recent versions of GNU Autoconf, Automake, Stratego/XT, and Doxygen. Do not forget to pass "--enable-bootstrap". Those requirements are not needed for compiling a nightly tarball.