Is Teradata GSS Client NT i386 version 15 a freeware or a licensed software?
Apparently yes, the Teradata Tools (package that includes the Teradata GSS client as well) are free to download. There has been no information related to the licensing options or anything that might be needed in case you plan to install the application. The developers specified on their website that the package you'll download is actually the full one.
Note: An account is necessary in order to download the setup package.