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Diffstat (limited to 'docs/LICENSE-MIXING')
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diff --git a/docs/LICENSE-MIXING b/docs/LICENSE-MIXING new file mode 100644 index 000000000..375f17aea --- /dev/null +++ b/docs/LICENSE-MIXING @@ -0,0 +1,83 @@ + License Mixing with apps, libcurl and Third Party Libraries + =========================================================== + +libcurl can be built to use a fair amount of various third party libraries, +libraries that are written and provided by other parties that are distributed +using their own licenses. Even libcurl itself contains code that may cause +problems to some. This document attempts to describe what licenses libcurl and +the other libraries use and what possible dilemmas linking and mixing them all +can lead to for end users. + +I am not a lawyer and this is not legal advice! + +One common dilemma is that GPL[*]-licensed code is not allowed to be linked +with code licensed under the Original BSD license (with the announcement +clause, unless there's a specified exception in the GPL-licensed module). You +may still build your own copies that use them all, but distributing them as +binaries would be to violate the GPL license. This particular problem was +addressed when the Modified BSD license was created, which does not have the +annoncement clause that collides with GPL. + +libcurl http://curl.haxx.se/docs/copyright.html + + Uses an MIT (or Modified BSD)-style license that is as liberal as + possible. Some of the source files that deal with KRB4 have Original + BSD-style announce-clause licenses. You may not distribute binaries + with krb4-enabled libcurl that also link with GPL-licensed code! + +OpenSSL http://www.openssl.org/source/license.html + + Uses an Original BSD-style license with an announement clause that + makes it "incompatible" with GPL. You are not allowed to ship binaries + that link with OpenSSL that includes GPL code (unless that specific + GPL code includes an exception for OpenSSL - a habit that is growing + more and more common). + +c-ares http://daniel.haxx.se/projects/c-ares/license.html + + Uses an MIT license that is very liberal and imposes no restrictions + on any other library or part you may link with. + +zlib http://www.gzip.org/zlib/zlib_license.html + + Uses an MIT-style license that shouldn't collide with any other + library. + +krb4 + + While nothing in particular says that a Kerberos4 library must use any + particular license, the one I've tried and used successfully so far + (kth-krb4) is Original BSD-licensed with the announcement clause. Some + of the code in libcurl that is written to deal with Kerberos4 likewise + have such a license. + +GSSAPI + + While nothing in particular says that a GSS/Kerberos5 library must use + any particular license, the one I've used (Heimdal) is Original BSD- + licensed with the announcement clause. + +fbopenssl + + Unclear license. Based on its name, I assume that it uses the OpenSSL + license and thus shares the same issues as described for OpenSSL + above. + +libidn http://www.gnu.org/licenses/lgpl.html + + Uses the GNU Lesser General Public License. LGPL is a variation of GPL + with slightly less aggressive "copyleft". This license requires more + requirements to be met when distributing binaries, see the license for + details. Also note that if you distribute a binary that includes this + library, you must also include the full LGPL license text. Please + properly point out what parts of the distributed package that the + license addresses. + +OpenLDAP http://www.openldap.org/software/release/license.html + + Uses a Modified BSD-style license. Since libcurl uses OpenLDAP as a + shared library only, I have not heard of anyone that ships OpenLDAP + linked with libcurl in an app. + + +[*] = GPL - GNU General Public License: http://www.gnu.org/licenses/gpl.html |