Asterisk and UniMRCP Licensing

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Hey all -

In some previous conversations on the Asterisk mailing lists, we
noticed that some users of Asterisk were using UniMRCP [1] with
Asterisk, as well as some modules made and distributed by that
project. Unfortunately, there were some licensing concerns with using
UniMRCP with Asterisk. As such, we contacted the UniMRCP project
regarding the licensing issues and, after discussing the issue with
them, we believe we have found a good path forward such that users of
Asterisk and UniMRCP can use both projects together without violating
the license of Asterisk.

As you may know, Asterisk is licensed under the GPLv2. When Asterisk
is statically or dynamically linked with a library, this creates an
overall 'derivative work' as referred to in the GPL. Barring an
exception, this means that any library Asterisk dynamically links with
must be licensed under a GPLv2 compatible license. Unfortunately,
UniMRCP is not licensed with a GPLv2 compatible license, as the Apache
2.0 license is not compatible with the GPLv2 [2]. This makes
distribution of modules that link with Asterisk and UniMRCP
problematic, as those modules technically should not be licensed under
the GPLv2 - and hence should not be used with Asterisk under the GPLv2

That being said, we really like the UniMRCP project, and think it a
great library for providing complex speech services. In the past, when
faced with similar situations, we've added specific disclaimers to the
licensing of the Asterisk project such that users are allowed to link
Asterisk with specific libraries and distribute the resulting files.
As such, we've modified the Asterisk license [3] to read the

"Specific permission is also granted to link Asterisk with OpenSSL, OpenH323,
UniMRCP, and/or the UW IMAP Toolkit and distribute the resulting binary files."

This should make it easier for participants of both projects to use
Asterisk with UniMRCP without violating the licenses of either

Hopefully this e-mail and the exception in the LICENSE file clears up
any ambiguity that people may have had regarding Asterisk and the
UniMRCP project.

Thanks -



Matthew Jordan
Digium, Inc. | Engineering Manager
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
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