Most of the products developed by Liferay are Open Source software. They are typically made available under the GNU Lesser General Public License (LGPL) which provides you with the four freedoms of free software:
The freedom to run the program as you wish, for any purpose.
The freedom to study how the program works and change it so it does your computing as you wish. Access to the source code is a precondition for this.
The freedom to redistribute copies so you can help your neighbor.
The freedom to distribute copies of your modified versions to others. By doing this you can give the whole community a chance to benefit from your changes. Access to the source code is a precondition for this.
Two words - more freedom
One important difference between the GNU Public License and the Lesser GNU Public License that most Liferay projects use is the exception for software that has a different license. While LGPL licensed projects themselves retain the benefits of being free software, if you build an application that does not modify the original code, you are in no way obligated to release your code under the LGPL. Instead, you are free to use any license you like: open source or proprietary, or none at all. In this way, Liferay preserves your freedom to release your software (or not) in any way that seems right to you.
Open Source is more than just the code
Liferay also follows a common (but not always true) collaborative model of Open Source software development. In particular:
Development tasks can be followed in real time in the issue tracking system of the project .
Source Code is made available as it is being written (most often on GitHub)