Clarify the GPL licence terms

[Matt Giuca]

The program, as found at http://www.bealecorner.org/best/gforge/, contains inconsistent application of the GNU General Public License. The archive includes a full copy of the GPL version 2. It is clearly licensed under version 2, but it is unclear whether it is "or any later version" or if it is 2 only.

The only source file which mentions a license is hl.c, which states "either version 2 of the License, or (at your option) any later version." All other source files have no license information (except for third-party modules; see below). The file hf-lab.hlp also contains the text "either version 2 of the License, or (at your option) any later version." This text is produced by the executable itself if the user types "warranty" at the prompt.

Unfortunately, the file README.TXT contains the text "the GNU General Public License, version 2," without invoking the "or any later version" clause. This is the only place where the "or any later version" clause is not invoked.

Thus it is unclear whether the author intended for the software to be licenseable under future versions of the GPL. I would argue that it is legal to apply later versions, as the software itself tells you this. But conservatively, we must assume that it is not covered by later versions. Only the original author can clarify this position.

There are also a number of third-party libraries which have been incorporated into the HF-Lab source code:
- crater.c: (Heiko Eissfeldt) GPLv2 or later.
- fftn.c: This has a very long history, apparently having started life as a Fortran program by R. C. Singleton in 1968 (http://www.netlib.org/go/fft.f). It was then ported to C by Mark Olesen (http://www.netlib.org/go/fft-olesen.tar.gz), who applied the GPL (doesn't say which version), and this version was copied to HF-Lab. Olesen later removed the GPL, settling on a generic permissive license, so perhaps switching to this later version would fix any ambiguities regarding the GPL. Assuming that the original Singleton version has no legal tangles, this is okay.
- gread.c, gwrite.c: From the GD library version 1.1.1. Has a generic permissive license on it.
- rand.c: "This C language version was written by Jim Butler, and was based on a FORTRAN program posted by David LaSalle of Florida State University." -- could be hard to track down the license on this.
- typy.c, x_iface.c: From Lab-3D. Has a generic permissive license.

Of these, only rand.c, and possibly the very early history of fftn.c, are questionably licensed.

The other files all appear to have been created by John Beale, and he has licensed those under the GPLv2, as discussed above.