[MetaCRS] Are we allowed to redistribute NADCON grid files?

[Martin Desruisseaux]

I downloaded the NADCON grid files from http://www.ngs.noaa.gov/PC_PROD/NADCON/ 
and I'm considering to include them in the JAR file of GeoTools referencing 
module, as an optional plugin. If I'm understanding right, it is in the public 
domain because it is U.S. government work, so I would be allowed to redistribute 
them in a JAR file providing that I give credit to National Geodetic Survey 
(NGS). Could someone confirm if I'm right or wrong please?

	Thanks,

		Martin