The fundamental problem is that the freeRADIUS project's PAM module is available under the GPL, and not under other licenses. It turns out that if the module is used in any proprietary products, then the GPL license infects the application due to the module being dynamically loaded during the course of the PAM invocation.
This is a problem for companies that wish to integrate PAM authentication without having to GPL their entire source base due to the infectious nature of the license.
The original module is taken from http://opensource.apple.com/ and depends on the dual licensed BSD/GPL package libpwdb. It will be modified to use the the FreeRADIUS client library, which is BSD licensed.
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