Open source software licenses, is a legal agreement between the author of the code (licensor) and the user (licensee). Generally the the author makes the software code available for free, but with certain requirements that the user must follow.
Generally, the open source license terms adhere to the user when the new software is distributed (through physical media, FTP, or on Github, or embedded in a commercial product like a TV) this generally means that if you are only using the software internally one may not be bound by the terms of the license. If you are using openly licensed software as part of a web based service as an application service provider (ASP), but not directly distributed the software some Open Software licenses may still adhere to your use.
Understanding software licenses is extremely important to both users and authors. If you use openly licensed code as part of your project you are legally responsible for complying with the terms of the license. If you license code that you have authored, and select the wrong license it may allow others, such as large for profit companies to leverage your project in ways you don't intend.
There are two primary flavors of Open Source Software licenses. Permissive licenses and Copyleft licenses.
Permissive software licensees are very similar to most Creative Commons licenses. Permissive licenses allow others to use code with few restrictions. Users are able to make changes, additions, and generally combine the code to create new programs. Users are also able to distribute the resulting programs, under the terms of the license.
For example the most popular permissive license the Apache License 2.0 requires distributed code that use the license to 1. state any major changes made to the original code and 2. include a copy of the notice file with attribution notes, along with the copyright notice and license text.
In addition to the Apache 2.0 License the other popular permissive licenses are the MIT License and the BSD (Berkeley Software Distribution) family of licenses of those the BSD 3-Clause is the most popular.
Copyleft licenses allow others to make changes, additions, and combine the code with compatibility licensed code to create new programs. Users are also able to distribute the resulting programs, but unlike with permissive licenses any derivative work is required to be licensed under the same license or a compatible (substantially same) license. In other words any derivative code has to as "open" as the original.There are strong copyleft and weak copyleft licenses.
Strong copyleft licenses require anyone who distributes works derived from the licensed code to make the work, and the corresponding source code available under the same license. Strong copyright left licensees apply to the entire software program included linked libraries and other components. Generally, strong copyleft licenses allow one to privately modify or use the code, so long as it is not publicly released. One exception to this is the Sybase Open Watcom Public Licence which requires that source code be published even when used solely for private study.
Weak copyleft licenses generally have the same requirements, but apply to a narrower set of code. If a user modifies or adds to the code and distributes the resulting work, like the strong copyleft license they are required to license the derivative work under the same license as the original. However if a program only uses weak copyleft licensed code, and keeps it as an unmodified separate file they can combine it with additional or modified code and distribute the resulting program under a different license.
The best known Strong Copyleft licenses are the GNU-General Public Licenses GNU-GPL or just GPL which has three iterations. Weak Copyleft licenses include GNU-Lesser General Public License (LGPL) and Mozilla Public License 2.0.
FreeWare is not a license and there is no agreed upon definition of user rights for FreeWare. Instead it is software or code that is generally distributed with out cost to the end user, but the underlying code is proprietary aka the default copyright rules: "all rights reserved." That generally means that there is no open license or End User License Agreement (EULA) that would allow you to re-use, remix, or otherwise modify the source code of the software. Every author defines its own rules for FreeWare it offers, so exceptions to this general rule may apply. .
