LGPL

The GNU Lesser General Public License (or LGPL for short) is a popular open source and free software licence. It allows re-use by non-GPL-compatible code (including non-open-source code) as long as inclusive code remains under the LGPL, or alternatively converted to the GPL.

As such the LGPL is a "weak" "copyleft" licence.

Links

 * The LGPL on the Wikipedia
 * The LGPL Homepage