You can download the source tarballs here. The releases are signed with the gpg key (8DFF53E18F2ABC8D8F3C92237EE0FC4DCC014E3D), which you can find gro.k1532233603limot1532233603pyrc@1532233603nsa-D15322336033E4101532233603CCx01532233603-gpg_key.asc">here or on any keyserver.
openSUSE and Fedora
RPM packages for openSUSE, SUSE Linux Enterprise and Fedora are available here.
A NSIS installer and zip archives of the latest version can be found here.
git clone git://git.libssh.org/projects/libssh.git libssh
git clone https://git.libssh.org/projects/libssh.git libssh
To start with git take a look at the Git Community Book.
You can browse it here.