Fluid Construction Grammar can be downloaded as part of the Babel2 software package on Github. Babel2 is a general cognitive framework that connects FCG with language technologies for conceptualization and interpretation, and with mechanisms for cognitive processing, learning, multi-agent interactions, and robotic embodiment.
The technical documentation for the Babel2 framework is available here .
About Babel2: Babel2 is written in Common Lisp and runs in most major Lisp implementations (ccl, sbcl, lispworks) on all major platforms (linux, mac osx, windows). Its source code is released to the public under the BSD License. Installation scripts are provided through the Github wiki.