The source distribution is available from http://www.sashanet.com/internet/download/cgi++-0.8.tar.gz. You will need a C++ compiler with STL support to build and use CGI++. A clean compile is guaranteed on Linux and GNU 2.7, others still need to be tested, but you are free to give it a try. Installation is simple:
gunzip -c cgi++-0.8.tar.gz | tar xvf -
cd cgi++-0.8.tar.gz
./configure
make
su (if needed)
make install