All the three mentioned above are three forms in which ‘free’ software are available in the online world. The three terms are used so interchangeably by people that their definitions in common usage have got mixed up. We will try to clear up what these three exactly mean and what are the differences.
Open source:
Open source is a type of software which is freely available and its source code is available for further development, modification and redistribution. Generally all open source softwares have a community of developers who provide support, documentation and even binary versions of the software to people who may be interested in it. These additional services, though, may not be free monetarily. The ‘free’ part here is to be taken as the ‘free’ in ‘free speech’ rather than in ‘free beer’. However, some open source products released under the ‘General Public License’ (GPL) are required to have free (as in ‘free beer’) source code as well.
There are several ongoing open source software projects. The open source nature of these projects means that there will be several people working on modifying and improving the software from around the world. Some such examples include the Web browser Mozilla Firefox, content management software like Drupal, Joomla etc.
Freeware:
Freeware is the type of freely available software whose developer decides to distribute it for free. In contrast to the open source software, the source code in this case is not available for modifications and further development. Also, it should be noted that the distribution of the software may also be restricted by its developer, often allowing users to download it from his site only. Many free to download applications are available on the Internet. It is always wise to read the license before downloading the software. Many people tend to unknowingly share such applications with other people, without realizing that this may actually be illegal.
Shareware:
Shareware is very different from these other forms of free software and to some extent also a misnomer. The authors of shareware maintain their full intellectual right over shareware. The only difference between shareware and other commercially available software is that in this case the software is available for freely for trial for a limited number of days, or a limited number of times. After the expiry of the ‘free’ period, the users of shareware are required to pay for it. Source code and collaboration communities which exist around open source projects do not exist in this case.