As software developers and publishers, when it comes to integrating third party software, we have to look carefully at the license. Since our products are commercial and not “free” (our code is closed), we only integrate third party software that have non-copyleft license. We provide below is a little explanation of copyleft versus non-copyleft, hoping that it can help some of our customers understand the difference.
Copyleft licenses are licenses that require redistributed copies and derivative works to be under the same license. In other words, the code is free to use, to share and modify but any resultant works must be distributed under the same license.
Most common copyleft licenses:
- GNU General Public License (GPL)
- GNU Affero Public License (AGPL)
Non-copyleft licenses permit the code to be incorporated in software or programs that are distributed under some other license, including a proprietary one.
Most common non-copyleft licenses:
- Apache License Version 2.0
- BSD license
- MIT license
- LGPL (?)
Though these licenses are considered permissive, they do come with some requirements, read more here.