Fluid Construction Grammar can be downloaded as part of the Babel software package at this link. Babel 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 Babel 2 framework is available here .
About Babel 2: Babel 2 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.