As you enter the world of server management, you are likely going to encounter free and open source software. Even a Windows system administrator these days will likely have to at least run Linux in a virtual machine at some point. Therefore, having a little background knowledge on how Linux and other open source software differs from proprietary software can be useful.
The following are 4 common open source licenses:
1. GNU GPL – Perhaps the most widely used, the GPL is also the most strict. While it allows anyone to freely use, download, distribute, modify or even sell the software, it also strictly requires that any redistribution carries the same license. Linux is famously licensed under GPL v2.
2. BSD – This type of license is considered more permissive. With it, you can essentially create a proprietary version of the software after you have performed your modifications. You are not required to release anything under the same license.
3. Apache – Similar to the BSD license, Apache allows for releasing your changes to the code under a difference license. It provides some additional legal information about copyrights, trademarks and patents that the BSD license does not explicitly mention.
4. GNU LGPL – Designed as a compromise for linking non-GPL libraries, the LGPL allows for linking with code that has a different license, but like the GPL itself, the code licensed under it must be re-released under the same license.