Bam is a fast and flexible build system. Bam uses Lua to describe the build process. It's takes its inspiration for the script files from scons. While scons focuses on being 100% correct when building, bam makes a few sacrifices to acquire fast full and incremental build times.
I think gendocs.py contains an error. I suppose
root.nodes += [ParseTextFile(Node("License"), "license.txt", True)]
should be
root.nodes += [ParseTextFile(Node("License"), "COPYING", True)]
Otherwise the script won't work.