About OSGeo4W license terms
While each program or package available from OSGeo4W has it's own license, they are all open source. For example GDAL/OGR is X/MIT, GRASS is GPL, and uDig is LGPL, to highlight just 3 prominent applications.
OSGeo4W itself only has two applications, pkg-setup and pkg-apt. All others are simply convenient re-packaging of projects from elsewhere. The PackageListing describes each of the packages and where they are acquired from. To determine a particular application's license terms examine the install package and/or the source projects' website.
An OSGeo4W CD aquired from somewhere other than the project website may or may not have other things on it with different, possibly proprietary, license terms. There is a page describing how to make your own installation cd.