Hi all, recently some RTnet user was worried again about using RTnet together with non-GPL compatible applications (typically commercially licensed). I pointed out what we always stated here:
There is no reason why using RTnet from a non-GPL user space application should be denied. Also, I do not recall any case where some copyright holder stated this more restrictively (originally, at least I considered even certain in-kernel setups OK, but I was still young at that time ;) ). However, when looking at the two headers you may need in your user space application, rtnet.h and sometime also rtmac.h, they do not imply this. Rather, they are explicitly licensed under GPL v2+. And there is no other exceptional notice in the RTnet source tree. In order to finally and clearly express the intended usage model, I picked up the license exception for headers that you can find in the Xenomai project, even passed it through the legal department of my employer and added it tentatively two the mentioned headers. Here is the diff of rtnet.h, rtmac.h would be extended likewise: diff --git a/stack/include/rtnet.h b/stack/include/rtnet.h index 9a325bc..4afa270 100644 --- a/stack/include/rtnet.h +++ b/stack/include/rtnet.h @@ -21,6 +21,24 @@ * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * + * As a special exception to the GNU General Public license, the RTnet + * project allows you to use this header file in unmodified form to produce + * application programs executing in user-space which use RTnet services by + * normal system calls. The resulting executable will not be covered by the + * GNU General Public License merely as a result of this header file use. + * Instead, this header file use will be considered normal use of RTnet and + * not a "derived work" in the sense of the GNU General Public License. + * + * This exception does not apply when the application code is built as a + * static or dynamically loadable portion of the Linux kernel nor does the + * exception override other reasons justifying application of the GNU General + * Public License. + * + * This exception applies only to the code released by the RTnet project + * under the name RTnet and bearing this exception notice. If you copy code + * from other sources into a copy of RTnet, the exception does not apply to + * the code that you add in this way. + * */ #ifndef __RTNET_H_ I still need to dig through the available logs, identifying the potentially affected copyright holders. So this is also a public call to all those who think to own some bits of the affected headers or user space API. Please state if you agree or disagree with the clarification. There is no schedule yet when to apply the change. Once the copyright owner recherche is done, I will define a grace period after which the change will be applied to give people I'm unable to contact another chance to reply. That said, no one already running RTnet aside a commercial application needs to be concerned. I'm not going to send any lawyer after you, even if you are using it in a kernel application. However, but that's nothing new, you should still reconsider your license situation in that case as there are a few more Linux kernel copyright holders and you may use more interfaces than just RTnet. Jan
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