You can download this from the github project.
FFIs (foreign function interfaces) are difficult. One, or even two, may be easy to write, but writing them for many libraries and maintaining them is a difficult problem.
If we were able to automatically generate FFIs and find reasonable generic interfaces to solve general problems with interacting with C code, we have a fighting chance at producing many FFis for Scheme. This is one area where Chicken Scheme has succeeded with easyffi.
This was my first attempt at something like Chicken Scheme's easyffi. It generates Gambit Scheme FFIs from C files using the SILex parser. It was simply a research project and has many deficiencies. I am deprecating this project in favor of a new one which will probably use gcc-xml (that project hasn't been started yet).