Hi, I just noticed this software; I use HDF(5) a lot, so this is definitely interesting to me...
I did notice one problem regarding the license, however. NCO is under the GNU GPL. HDF(4) and NetCDF are under their own licenses (e.g. http://www.unidata.ucar.edu/packages/netcdf/copyright.html\) which contain a BSD-like "advertising clause" (any advertisements for software using them must mention them). This is incompatible with the GPL (see http://www.gnu.org/philosophy/bsd.html\). (By design, the GPL is incompatible with code under any licenses whose restrictions are not a strict subset of its own; that's the whole point, to prevent someone from adding features under a more restrictive license.)
Any binaries of NCO are legally derived works of both the NCO source *and* the relevant libraries, and must obey the terms of both...but this is impossible, since the two are contradictory. Because of this, people other than the NCO copyright holders themselves technically have no legal way to distribute NCO. (This is what caused the continuing KDE controversy, e.g. with Debian.)
The fix is simple. You are the copyright holders of all the NCO code (right?), so you can change the license anyway you want. Just add a couple of lines explicitly giving permission to link to NetCDF and HDF(4) and distribute the resulting binaries. Something like:
Copyright (C) 1995--2000 Charlie Zender
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
As a special exception to the terms of the GPL, you are permitted
to link the NCO source code with the NetCDF and HDF libraries
and distribute the resulting executables under the terms of the GPL,
but in addition obeying the extra stipulations of the NetCDF and
HDF library licenses.
Since this is such a simple fix, and merely makes your obvious intention explicit, I hope that you will consider it. (I am familiar with licensing issues from experience in the free software community, distributing my own programs, and in talking with lawyers. I am not a lawyer, however. You might want to run the exact wording by the FSF at gnu@gnu.org to make sure it is the proper legalese.)
Cordially,
Steven G. Johnson
PS. You could honestly say that there's no practical problem because you're not about to sue anyone for distributing NCO executables. One problem is that if some Evil Company were to try to make proprietary enhancements to some GPLed program, they could just put all of their own files into a library, link to it from the program, and say in a courtroom that the GPL is commonly understood to allow that ("just look at foo and bar, which have been around for years").
PPS. Note that the HDF5 license was changed, the advertising requirement removed (changed into a "request"), specifically in order to make it compatible with the GPL.
PPPS. I am not trying to start a flame war...I am just trying to make you aware of the issues.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi, I just noticed this software; I use HDF(5) a lot, so this is definitely interesting to me...
I did notice one problem regarding the license, however. NCO is under the GNU GPL. HDF(4) and NetCDF are under their own licenses (e.g. http://www.unidata.ucar.edu/packages/netcdf/copyright.html\) which contain a BSD-like "advertising clause" (any advertisements for software using them must mention them). This is incompatible with the GPL (see http://www.gnu.org/philosophy/bsd.html\). (By design, the GPL is incompatible with code under any licenses whose restrictions are not a strict subset of its own; that's the whole point, to prevent someone from adding features under a more restrictive license.)
Any binaries of NCO are legally derived works of both the NCO source *and* the relevant libraries, and must obey the terms of both...but this is impossible, since the two are contradictory. Because of this, people other than the NCO copyright holders themselves technically have no legal way to distribute NCO. (This is what caused the continuing KDE controversy, e.g. with Debian.)
The fix is simple. You are the copyright holders of all the NCO code (right?), so you can change the license anyway you want. Just add a couple of lines explicitly giving permission to link to NetCDF and HDF(4) and distribute the resulting binaries. Something like:
Copyright (C) 1995--2000 Charlie Zender
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
As a special exception to the terms of the GPL, you are permitted
to link the NCO source code with the NetCDF and HDF libraries
and distribute the resulting executables under the terms of the GPL,
but in addition obeying the extra stipulations of the NetCDF and
HDF library licenses.
Since this is such a simple fix, and merely makes your obvious intention explicit, I hope that you will consider it. (I am familiar with licensing issues from experience in the free software community, distributing my own programs, and in talking with lawyers. I am not a lawyer, however. You might want to run the exact wording by the FSF at gnu@gnu.org to make sure it is the proper legalese.)
Cordially,
Steven G. Johnson
PS. You could honestly say that there's no practical problem because you're not about to sue anyone for distributing NCO executables. One problem is that if some Evil Company were to try to make proprietary enhancements to some GPLed program, they could just put all of their own files into a library, link to it from the program, and say in a courtroom that the GPL is commonly understood to allow that ("just look at foo and bar, which have been around for years").
PPS. Note that the HDF5 license was changed, the advertising requirement removed (changed into a "request"), specifically in order to make it compatible with the GPL.
PPPS. I am not trying to start a flame war...I am just trying to make you aware of the issues.
OK by me, I'll change the license as you suggest in the next version if
nobody has any disputes with it in the meantime...
Charlie
p.s., I do appreciate your intentions in pointing this out and
thanks for providing the sample text to fix the problem