There are lot of improvements and fixes since last stable release. There is much improved support for Samsung, Siemens and Motorola phones, new features in SMSD (message filtering, injecting for FILES mode) or support for OpenCellID.
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.
9f254bbdcc67f6efe377b85b2951d99baf73ca19563929e15257e9d40dfc0be9
7ed9bc8c107013b8aa19f94da68457278d78897f06eb20eb0a9713f975f1dbe2
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.
fe06fc82628a1508b0a229b7416bc3ccd8805c80057ac50fdc88988296b0bb90
e1fd1ec1cae3caba59cd3ba438aef950ceabeed5667e330a84d1a86bd021bd74
161ad5f99aba8bcea59c4be42e10c451939ecf651842b6d44eac8d4dba1bdb49
637166d76544f90403d26dd7e9ff56cf1767bf22e23e8f41d5333f6a19b91461