You can re-license any work that allows re-licensing. These include all
public-domain works, and any other works whose license terms allow it, such
as works under the BSD and X licenses. You can, for example, put the GPL
on any X-licensed work _in_addition_ to the X license. Your modifications
will clearly be under the GPL, but you will probably not be able to enforce
the GPL on the base work.
In the case of NEC, the Government's copyright appears to be illegal.
You can attempt to treat it as a public domain work if you want to be
the test case in court.
Thanks
Bruce
