GNU General Public License v2.0 or later
Covers both the GPL-2.0 (the "historical" free software license), the GPL-3.0 and possible later versions. Supported by a strong community (the Free Software Foundation - FSF). Copy, modification and distribution authorised. Changes/dates must be traced in source files. Any derivative must also be made available under one or more of these GPL versions. Compatibility / interoperability are known sources of tension when a project combines the covered code with non-GPL sources from other stakeholders, because according to the FSF linking other software to GPLed works extends the GPL coverage to…