viral license

This is also known as a Viral license.

Viral license is a copyright license that allows derivative works only when licensed under a compatible license to the original.

Viral licenses (such as the GNU General Public License)

This can lead to problems when software is derived from two or more sources having incompatible viral licenses in which the derivative work could not be re-licensed at all.

According to Free Software Foundation compliance engineer David Turner, the term viral license creates a misunderstanding and a fear of using copylefted free software.

Copyleft licenses are sometimes referred to as "viral licenses" because any works derived from a copyleft work must themselves be copyleft when distributed (and thus they exhibit a viral phenomenon).