I am sure every one of you would known what open source software means. Even if you never thought about it you would most likely be using one or more of them in your day to day life.  Each of these open source software come with a license agreement which we usually click on “I agree” without reading it and proceed (because it is free and we dont care about anything when we get something for free ).  If you have done that but did not know what are the licenses governed by these open source programs and what they mean, then you better be aware of it.  It is the least that you can do to all those developers who put in their effort to make your life easy, for free.  Some of the famous licenses I have briefly described here with the links to the original license.

• GNU General Public License (GPL) - This license basically authorizes the user to use the program, view, modify, improve and redistribute the program under the same license.
• Lesser General Public License (LGPL) - This is same as GPL except that it allows the program to link to other programs which could be licensed under GPL/LGPL or could be proprietary too.
• Apache Software License (ASL) - License to use, view, modify, improve, redistribute and even sell modified version but include the original files that comes with the Apache License.

There are numerous other open source licenses available. The list of approved open source licenses can be found in OpenSource.org, which is a non-profit organization to manage and promote open source. Take a look at this quick comparison of the most widely used open source licenses for what it stands for.