Open Source Needs To Clean Up Its Language

Simon Phipps | InfoWorld | November 1, 2013

The licensing terms 'weak copyleft,' 'strong copyleft,' and 'permissive' are confusing. Here are my proposed alternatives

Open source licenses are all different, but they are often categorized according to an important attribute. Some open source licenses implement a clever hack invented by Richard Stallman where as a condition of the copyright license, anyone creating derived versions has to agree they will license the new version the same way as the original. In a play on words, this concept is called "copyleft."

In its strongest form, this "copyleft" idea can place a condition on the licensing of all the other code compiled together to make the eventual binary executable program. Complying with this requirement can be complicated (and expensive); as a consequence, many commercial software developers avoid the strongest forms of copyleft licensing.

There are less stringent forms of copyleft. Licenses like the MPL (Mozilla Public License) and the CDDL (Common Distribution and Development License) only require individual files that are modified to be licensed under the same license as the original and don't extend that requirement to other files used to build the executable. This is sometimes called "weak copyleft."