HISTORY ------- The DJVULIBRE-GSDJVU source code distribution is derived from the ATT-GSDJVU code released on the AT&T Labs Research web site under the terms of the Common Public License Version V1.0 (CPL) in June 2005. LICENCE ------- Since DJVULIBRE-GSDJVU is derived ATT-GSDJVU, it is distributed under the terms of the Common Public License V1.0 (CPL). The full text of the CPL is available in file COPYING.CPL. The differences between DJVULIBRE-GSDJVU and ATT-GSDJVU have been contributed by Leon Bottou. Recipients of the DJVULIBRE-GSDJVU source code distribution can use and copy these differences under the terms of the GNU General Public License, either version 2 of the License, or (at your option) any later version. The full text of the GPL is available in file COPYING.CPL. In consequence, should AT&T decide to authorize the redistribution of ATT-GSDJVU under the terms of the GPL, the DJVULIBRE-GSDJVU source code would also be fully available under the terms of the GPL. LICENCE INCOMPATIBILITY ------------------------- The CPL a genuine free software license that is unfortunately incompatible with the GPL. Both ATT-GSDJVU and DJVULIBRE-GSDJVU contain the source code of a driver for the GHOSTSCRIPT program , which is often distributed under the terms of the GPL . Although both DJVULIBRE-GSDJVU and the GHOSTSCRIPT source code are available under free software licenses, the license incompatibility is a serious problem. We reproduce below the Free Software Foundation comments on the CPL: +----------------------------------------------------------------------+ +------excerpt from http://www.gnu.org/licenses/license-list.html------+ +----------------------------------------------------------------------+ | | | Common Public License Version 1.0: | | | | This is a free software license but it is incompatible with the GPL. | | | | The Common Public License is incompatible with the GPL because it | | has various specific requirements that are not in the GPL. | | For example, it requires certain patent licenses be given that the | | GPL does not require. (We don't think those patent license | | requirements are inherently a bad idea, but nonetheless they | | are incompatible with the GNU GPL.) | | | +----------------------------------------------------------------------+ The requirements of the CPL, including the incompatible requirements identified by the FSF, are detailed in section 3 of the CPL. These requirements only apply to the redistribution of CPL licensed programs. Therefore we believe that anyone is free to download both the DJVULIBRE-GSDJVU and GHOSTSCRIPT source code packages and to use them as they see fit. In particular, anyone can combine and compile these source code packages. However, it is not possible to redistribute the GSDJVU executable, because it is not possible to satisfy the redistribution requirements of both the CPL and the GPL. The above statement is merely the expression of our belief. It should not be understood as a guarantee of any kind. Copyleft license compatibility is a complicated issue. You must form your own opinion before using DJVULIBRE-GSDJVU. HOW TO FIX THIS UNFORTUNATE SITUATION ? --------------------------------------- First of all, you should not ignore the current licenses. In particular, we strongly advise you against redistributing combinations of DJVULIBRE-GSDJVU and GHOSTSCRIPT to anyone. The only practical way to solve the incompatibility issue is to politely ask our AT&T friends to clarify their intentions. Please send a brief email to AT&T's Intellectual Property Licensing organization with a copy to . - First thank them warmly because they worked very hard and used their hard earned professional credit to help release GSDJVU under a free license. - Second give your best argument to justify authorizing the redistribution of GSDJVU under the GPL. Here are a few examples: * Whatever the purposes of the ATT-GSDJVU open source release are, this purpose would be better served by licensing terms that facilitate the use of GSDJVU. * Legally, what does it mean to release a source code (ATT-GSDJVU), whose operation technically depends on a second program (GHOSTSCRIPT), under terms that are incompatible with those of this second program. Alas, nothing suggests that this problem will be fixed immediately. Our AT&T contacts indicate that they currently have other priorities or policies. Yet, priorities and policies change with time. OTHER USES OF GSDJVU BESIDES DJVU --------------------------------- In return we would like to drop a few ideas on commercialy feasible uses of the GSDJVU technology besides DJVU compression. Do not hesitate to contact AT&T's to commercially license GSDJVU for such purposes. GSDJVU is a very powerful technology that analyzes each page of an electronically generated document and decomposes it as (1) a low resolution continuous color background image, and (2) a collection of high resolution foreground objects having each a single flat color. Such a decomposition can be very useful: * PDF Optimization --- The quality and size of PDF files vary dramatically according to the quality of the input material. The GSDJVU decomposition is a good basis to significantly reduce the size of badly authored PDF files. * Printing --- Most printers represent colors with dithering. Large dithering patterns give accurate colors at the expense of resolution. Small dithering patterns give coarser colors with higher resolution. The GSDJVU decomposion neatly identifies which parts of a page are best printed using small or large dithering patterns. * Helping vision challenged persons --- The GSDJVU decomposition allows for dimming graphical embellishments that make reading difficult and enhancing the contrast of the meaningful text and graphics.