THE LAY OF THE LICENCE LAND
Since licensing is a confusing issue for developers new to open source, GitHub created a helpful website at https://choosealicense.com. Besides recommending MIT for those wanting to keep things simple, and GPLv3 for those that want something closer to Free Software ideals, the website has helpful advice on which licences are preferred by what communities. There’s also a summary of some of the more widely used licences, such as the Apache License 2.0 (which allows limitations on trademark use) and the “mediumcopyleft” Mozilla Public licence.
There are probably more open source licences than there are things in Horatio’s philosophy, and it wouldn’t really be useful to list them in all their clause-ey glory here. Some, such as the Creative Commons family, have been penned with crafts other than software in mind. There’s also the GNU Free Documentation License (GFDL) under so many of those man pages you’re supposed to flipping read. We won’t even mention the profane WTFPL licence.
But it is important to note that they all arose out of some need, and, as we tell anyone who complains that there are too many Linux distros, if people are willing to take the time to write quality FLOSS then they have every right to release it under whatever terms they like.
The first version of the GPL appeared in 1988, and by 1991 so too had the GPLv2 and the GNU Library GPLv2. The Library licence permitted linking GPL’d libraries into proprietary executables (under certain conditions) since precluding this would discourage use of those libraries in favour of non-free alternatives. The Library GPL was renamed to the GNU Lesser General Public License in 1999, and is still popular today.