LICENSE.txt

The full tagger software package is licensed as GPL version 2 or later -- at
least, according to our interpretation of how the GPL works, which we find
confusing, so you should conduct your own legal analysis if this is important
to you.  The details are as follows.

src/ -- All original code we've written -- the files in src/ with one
exception below -- we license under the Apache License version 2.0. However,
we have several GPL'd dependencies that we include in this package, which,
as we understand it, force the full package to be GPL.

src/cmu/arktweetnlp/impl/OWLQN.java -- is licensed GPL, originally from the
Stanford POS Tagger version 2010-05-26.  It can be removed and the tagger
works just fine with a pre-trained model (but you can't retrain).  We are not
aware of an interpretation of the GPL for whether it infects through trained
models.

lib/stanford-postagger-2010-05-26.jar -- license GPL.

lib/posBerkeley.jar -- licensed Apache 2.0 (see below).

lib/trove-3.0.0a5.jar -- licensed LGPL.

(There are many more libraries used in the released version, that have their
own licenses and not listed here.)

... It is possible to remove the GPL'd dependencies, which are somewhat
minimal, but we have not done so at this time. We suspect it won't matter
for the vast majority of use cases, but would be interested in hearing from
you if otherwise.

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GPL version 2:
http://www.gnu.org/licenses/gpl-2.0.html

Apache version 2.0:
http://www.apache.org/licenses/LICENSE-2.0

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posBerkeley.jar is Copyright 2011, Taylor Berg-Kirkpatrick.  Licensed as Apache 2.0:

    From: Taylor Berg-Kirkpatrick
    Date: Thu, 30 Jun 2011 15:33:03 -0700
    Subject: Re: license for your code
    To: Kevin Gimpel

    Sure. I give you guys permission to release under Apache.

    On Tue, Jun 28, 2011 at 11:50 AM, Kevin Gimpel <kgimpel@cs.cmu.edu> wrote:
    [...]
    > Dipanjan, Brendan, and I are working on the release of our group's Twitter
    > part-of-speech tagger and we are now trying to figure out what license to
    > use with the code that we are releasing. We extended code that you shared
    > with Noah last summer
    [...]
    > But in order to do this, we'd have to ask you to "release" that same code
    > you gave to us under an Apache license.

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