Principles of Programming Languages is Copyright © 2002-2009 Scott F. Smith and is released under the GNU Free Documentation License.
FbDK is a framework for writing the interpreters discussed in the book. The binaries are fully working versions of the interpreters, but the source distribution is simply the framework with a dummy implementation of the interpreters. The source distrubition is released under the same license as the book. The binaries may be downloaded and freely used, but we reserve all rights to the binaries themselves and the source code from which they were produced.