Runbox Solutions works closely with, and is partially owned by, Copyleft Solutions AS.
In 1984/5 programmer Don Hopkins sent Richard Stallman a letter labeled "Copyleft—all rights reversed".
Sleepycat distributed Berkeley DB under a proprietary software license that included standard commercial features, and simultaneously under the newly created Sleepycat License, which allows open source use and distribution of Berkeley DB with a copyleft redistribution condition similar to the GNU General Public License.