Linking w/ GPL is always OK, but not redistribution [was: kde-xemacs or gnome-xemacs?]

Possibly a good place to get information about this is on the Free Software Business list, fsb(a)crynwr.com. To subscribe, fsb-subscribe(a)crynwr.com. A point about topic: FSB does not prohibit discussion of licenses, obviously, but it is primarily interested in their impact on different business models for free software, and not in legalisms. Disclaimer: IANAL. Glynn> I was under the impression that the only licence which was Glynn> 'GPL compliant' was the GPL itself. I'm not even sure that Glynn> it's legal to link GPL'd code against LGPL'd code (reasoned Glynn> arguments to the contrary would be appreciated). You can link anything you want to anything else you want, as far as the GPL is concerned. Even this is somewhat undesirable in theory: Stallman (private mail, but presumably also in public) somewhat regrets this but concedes the primacy of privacy for undistributed modifications. The reason he regrets it seems to be that companies like AOL and Yahoo[1] consider their mods to sendmail and Apache httpd respectively to be competitive advantages, and do not redistribute them.[2] Although neither example is GPL, RMS would like to forestall similar occurances with GPL'd software. The question is, under what terms can you distribute it? If some of the code (Linux kernel) is GPL, and other code (device driver) is under NDA, you cannot distribute the device driver linked, AFAIK. You can't distribute it statically linked into the kernel, and you can't distribute it as a module, either, because it is a derivative work (let's stipulate that; I am aware there are arguments against) of the Linux header files, some at least of which are GPL. This is also true of the Aladdin Free Public License. Aladdin has had to stop distribution of GNU-readline-enabled Aladdin Ghostscripts[3] on several occasions, and several drivers are distributed only in source form because they are GPL'd. (Of course, GNU Ghostscript can be distributed in binary form with readline or those drivers linked in.) If some of the code is GPL, and some of the code is XFree-style licensed, you can distribute binaries under the GPL. You cannot distribute it under an XFree-style license. I believe that if you link GPL code against LGPL code, you must distribute the LGPL code under the GPL. You can of course point to the site where you got the LGPL code and inform users that they can get the LGPL code under less restrictive conditions. You could even distribute two copies of the LGPL source, as a mere aggregation - they would differ only in the file COPYING ;-) But to distribute the code under the LGPL, you'd have to make a separate copy. That's absurd, I think. But the law is an ass. Footnotes: [1] I don't know for sure about either of them, it's hearsay. These are examples to make the principle clear. [2] Tim O'Reilly has written an open letter on this subject, it may be somewhere on http://www.opensource.org/, but maybe not, I can't find it right now. Maybe it was posted to FSB. [3] This is a useful-enough feature that Peter is considering removing the readline patches from the Ghostscript source distribution because they constitute an "attractive nuisance." People keep independently rediscovering that way to violate the GPL. -- University of Tsukuba Tennodai 1-1-1 Tsukuba 305-8573 JAPAN Institute of Policy and Planning Sciences Tel/fax: +81 (298) 53-5091 __________________________________________________________________________ __________________________________________________________________________ What are those two straight lines for? "Free software rules."