GRASS has been developed for over a decade as completely unrestricted public domain source code and executables. Though there was initial resistance to the existence of such robust software in the public domain, many competitors learned to take advantage of GRASS. It has reputedly been the intellectual stimulus for several enhancements to other GISs. Several companies conducted business by installing and customizing public domain GRASS for customers, and by providing other value-added services such as data base development.
As USA/CERL no longer supports the public version of GRASS, users are free to use what currently exists. They're also currently completely on their own. At least where the public domain version is concerned.
There is a commercial version of GRASS, adapted from the public domain version by Logiciels et Applications Scientifiques (L.A.S) Inc. of Montreal. In a recent check, LAS sold its GRASSLAND for Sun, Linux and Windows NT. LAS is trying to encourage the continuation of a robust public domain Linux, partly as a source of new ideas and code for their own developments.