I'm a little confused. If this software was
developed by NASA to begin with
and is unclassified, shouldn't it be in the public domain anyway, having
been developed with taxpayer dollars?
Not necessarily. Making software public costs time and money. Much of the
software developed by NASA really doesn't have widespread application.
Some of it is too sensitive for release, such as the onboard software
for HST. Some of it is subject to export restrictions. Some of it is
classified.
Eric