"The NCBI Software Development Toolkit was developed for the production and
distribution of GenBank, Entrez, BLAST, and related services by NCBI. We
make it freely available to the public without restriction to facilitate the
use of NCBI by the scientific community. However, please understand that
while we feel we have done a high quality job, this is not commercial
software.
The documentation lags considerably behind the software and we must make any
changes required by our data production needs. Nontheless, many people have
found it a useful and stable basis for a number of tools and applications.

The toolkit is available by anonymous ftp from ncbi.nlm.nih.gov"

excerpt from NCBI toolkit README file.

-- Tony Maher <tony.maher@ebioinformatics.com>
   FreeBSD bio-porters <bio@freebsd.net>