After almost two months of not so heavy development, here is another testing release. It just contains collected bug fixes, but there are still several problems outstanding so we're not close to the stable release.
You are downloading Gammu source code. To compile it you need some development environment for your platform and CMake tool to configure the sources. There are also some optional requirements for additional features which are listed in INSTALL file in sources. This file also contains more detailed instructions about compiling Gammu.
This source tarball contains Gammu command line utility, libGammu library and Gammu SMSD.
You are downloading Gammu installer for Windows. There is 32-bit version, 64-bit version and 32-bit version compiled with MSVC 9.0 to be compatible with Python 2.7.
You might need to install Visual C++ Redistributable Packages to run Gammu.