Microsoft airs tools' source code online

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Differences between GPL and CPL

I'm not a lawyer, but it appears that the GPL requires that anyone distributing GPL-licensed software, including derivative software (software that incorporates both GPL-licensed code and private improvements/additions to that code), must offer the resulting (new, improved) software under the GPL license, and ONLY the GPL license. Therefore, all such improvements/additions become part of the ever-growing body of GPL-licensed software. That's part of the whole idea of the GPL.

By contrast, the CPL allows commercial entities to offer CPL-licensed software, including derivative software, under their own license, so long as that license meets certain requirements set out in the CPL license, including that it must meet all of the terms and conditions of the CPL license. This means, as the CPL license points out, that the commercial entity could offer some kind of warranty, or technical support, for example.

Even more significantly, it appears that the CPL allows the developer of private improvements/additions to CPL-licensed code to license those improvements/additions separately under any type of license they choose. The CPL-licensed portions of their derivative software product must be licensed under a CPL-compatible license, but the improvements/additions may be kept proprietary. This derives from the definition of "Program" at the beginning of the CPL. Specifically, it states:

"Program" means the Contributions
distributed in accordance with
this Agreement.

If the improvements/additions are not distributed in accordance with the CPL, then they are not part of the "Program", and are therefore not subject to the CPL.

For example, if Microsoft were to incorporate in Windows XP a clever implementation of a memory-mamangement technique that it found in some GPL-licensed software, Microsoft would, under the GPL, be required to offer ALL of Windows XP under the GPL (the idea being that the rest of Windows XP would be an improvement/addition to the memory management code).

By contrast, if Microsoft were to do the same with code found in CPL-licensed software, they would NOT be required to offer any of Windows XP under the CPL license except for the borrowed code itself.

None of this is surprising, given that none other than IBM developed the CPL. They weren't trying to protect Microsoft; they were trying to protect themselves from being forced to give away proprietary software merely because it may include CPL-licensed code.

In case you're wondering, neither Microsoft nor IBM have ever been either my employer or my client. I have, however, had one friend who once worked for IBM.

Posted by: dbkennerly@...   Posted on: 04/08/04 You are currently: a Guest | Members login | Terms of Use

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