curl / Mailing Lists / curl-library / Single Mail


libcurl license incompatible with GPL 2?

From: Hauke Duden <>
Date: Sun, 10 Jun 2018 08:43:15 +0000

Hello everyone,

I have recently looked at the GPL compatibility of various open source licenses and I have my doubts whether the libcurl license is compatible to GPL v2.

By "GPL compatible” I mean that libcurl can be incorporated by a GPL project and the resulting combined work can be licensed under GPL.

The libcurl license is based on the MIT license and the normal MIT license is compatible with both GPLv2 and GPLv3. But the curl license has an additional clause at the end that places an additional restriction on the user of the library (namely not being allowed to use the author's names for advertising).

GPLv3 allows for such additional restrictions. But the older v2 version of the GPL states that no additional restrictions beyond what is included in the GPL can be placed on the users of the software. In my understanding that would make libcurl incompatible with GPLv2.

Note that the Apache license is also considered to be incompatible with GPLv2 for similar reasons (see

Do you have any comments about this issue?

Is GPLv2 compatibility even something that is desired for libcurl? I.e. is this be a “bug” in the license, or is this intended? Or maybe I am misinterpreting the legal implications of the license?

Best regards,


Received on 2018-06-10