Hi All, I figure I will through in my 2 cents worth of interpretation for their License, Restrictions and my Conclusions in regards to UPX. UPX and UCL are copyrighted software distributed under the terms of the GNU General Public License (hereinafter the "GPL"). Good, the program and compression library are distributed under the GPL (version 2 or later). The stub which is imbedded in each UPX compressed program is part of UPX and UCL, and contains code that is under our copyright. Okay, the stub that gets embedded into the program being compressed is under the GPL. The terms of the GNU General Public License still apply as compressing a program is a special form of linking with our stub. Hmmm, whatever. They are just making up a definition for the interaction between the stub and the program that is being compressed. A little weird but that is fine. They can define things however they want as long as they are clear about it. I could define the process used in my programs to perform buffered file I/O as pizza dough kneading. That would be fine as long as I am consistent. But it would not actually make it any sort of dough kneading. Only what I would be calling it in a license and documentation. So, they can call it a “special form of linking”. However, it does not make it any form of linking as understood by the rest of the world. As a special exception we grant the free usage of UPX for all executables, including commercial programs. See below for details and restrictions.
Yippie. You can use UPX with any program regardless of the license for that program. But, they are some exceptions and restrictions. The stub which is imbedded in each UPX compressed program is part of UPX and UCL, and contains code that is under our copyright. The terms of the GNU General Public License still apply as compressing a program is a special form of linking with our stub. Hereby Markus F.X.J. Oberhumer and Laszlo Molnar grant you special permission to freely use and distribute all UPX compressed programs (including commercial ones), subject to the following restrictions: Okay, I think this “special form of linking” is to establish the fact that it is not “traditional linking” and your program and the stub used for decompression are two separate programs with two different licenses. You program can have whatever license you want. But, the little stub that is embed into your program is a separate entity and has its own license that is not changed by the license used by the program compressed. 1. You must compress your program with a completely unmodified UPX version; either with our precompiled version, or (at your option) with a self compiled version of the unmodified UPX sources as distributed by us. So, if you are using UPX to compress a program that is not open source, you cannot use a modified version of UPX. This implies that if your program is open source, you can change UPX however you want. 2. This also implies that the UPX stub must be completely unmodfied, i.e. the stub imbedded in your compressed program must be byte-identical to the stub that is produced by the official unmodified UPX version. Hmmm, this implies that programs which are not open source must use a version of the UPX stub that is identical to the officially released version. Therefore, any changes or compile time options which may result in changes to the binary code of the stub cannot be used with programs that are not open source. 3. The decompressor and any other code from the stub must exclusively get used by the unmodified UPX stub for decompressing your program at program startup. No portion of the stub may get read, copied, called or otherwise get used or accessed by your program. Alright, if your program is not open source, you can use the UPX stub. But, that’s it. Fine, nobody does anything with the stub directly anyway. Although this clause would technically exclude any commercial operating system from executing a program that had been compressed with UPX, that is not what is meant. There is what is known as “the letter of the law" and "the intent of the law.” Anyone reasonable would conclude, since they provide versions of UPX for Windows, they do not intend it not to be usable on a commercial operating system. Furthermore, they would not be excluding “normal use” of any program compressed with UPX. The License is dated 2/25/2000 making it almost a 1/4 of a century since it was last modified. Now looking at the README.SRC file, we find some additional information… The precompiled UPX versions are linked against the NRV compression library instead of the UCL library. Using the same compression algorithms, NRV achieves a better compression ratio. NRV is not publicly available, though, and probably never will be. While you may be disappointed that you don't have access to the latest state-of-the-art compression technology this is actually a safe guard for all of us. The UPX source code release makes it very easy for any evil-minded person to do all sort of bad things. By not providing the very best compression ratio it is much more difficult to create fake or otherwise disguised UPX versions (or similar trojans), as any end user will notice when the compression has gotten worse with a new "version" or "product". Finally please be aware that you now have your hands on the source code of the most sophisticated executable packer ever. Let's join our forces to make it even better :-) Hmmm. So, the official UPX binaries are not linked to the UCL library which is GPL. The reason for using a different library is “security through obscurity” which does not work. However, this also means that the official build of UPX is not open source. It is freeware. However, this freeware version can be used to compress any program, regardless of the license for that program. This also means that it is possible that the open source version of UPX using the UCL may not be used to compress any program that is not open source. Because, the stub might not be byte identical to the stub created by the NRV library. If so, it would be in violation of the License agreement. Obviously, I am not a lawyer. But, what I gather from all of this nonsense is the following… For the FreeDOS distribution, it really does not matter if we use the official build of UPX with NRV or the strictly GPL version with UCL compression. Any of the programs we might compress will be open source and can use either version. For the end users of our release, it could matter. If those users decide to provide freeware or commercial software compressed with UPX they must use the byte identical stub that is provided with the official build of UPX. If the stub that is stapled into their executables is different with the UCL version, they would be in violation of the UPX License. This is something to consider when determining which version of UPX is provided with the FreeDOS distribution. :-) Jerome
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