Software Licensing

Types of Licences

1. Proprietary e.g. Microsoft Windowss
2. Copyleft (FOSS) - GNU General Public License, CC BY-SA e.g. Linux kernel, GCC
   2.a GNU LGPL e.g.
3. Permissive (FOSS) - BSD License, MIT License, Apache License, CC BY e.g. Apache Web Server
4. Public domain - WTFPL, CC0

If the conditions specified by the license are not met, then it results in copyright infringement.

Open source software vs. Free software

Free software focuses on the freedom to run, copy, distribute, study, change, and improve a software. Think of free speech and not free beer. Their enemy is proprietary software released by companies such as Microsoft and Apple.

Open source focuses on the effective collaborative of software development. Remember the Cathedral vs. Bazaar analogy.

The underlying idea between the two terms is different. A neutral term is FOSS or FLOSS. e.g. Linux kernel.

FOSS Licenses

Two types of FOSS licenses are copyleft (more restrictive) and permissive (less restrictive). Copyleft vs. Permissive

A copyleft license ensures that anyone who receives the binary version of the software is entitled to the source version (including any source modifications that went into any binaries they received), and that person, in turn, is also required to pass down the four freedoms to anyone else that they pass said binaries/code on to.

A non-copyleft FOSS license could allow one person to receive the four freedoms as part of obtaining a copy of the code, but then that person can choose whether they want to give the four freedoms (or any individual one of the freedoms) to someone else that they give the software to.

It's important to keep in mind that non-copyleft licenses can transform from being free/open source software to non-free, non-open source software licenses, because the enforcement of the preservation of the freedoms is not in place.

GNU GPL vs. GNU LGPL

GNU project has two licenses for its libraries. The important difference between the two is that using the Lesser GPL permits use of the library in proprietary programs; using the ordinary GPL for a library makes it available only for free programs.

So when is LGPL useful? LGPL is useful especially when the library's features are readily available for proprietary software through other libraries. With LPGL, such free library's get more users.

So when should LGPL not be used? However if the library's features are not readily available elsewhere, then LGPL should not be used because it goes against the principles of free software. GPL should be used in this case because it leads to the development of more free software, and encourages free software movement.