As per wikipedia, “Open-source software (OSS) is computer software that is available in source code form, for which the source code and certain other rights normally reserved for copyright holders are provided under a software license that permits users to study, change, and improve the software.” Or in other words, Open Source free software is a code or application which is created by a open community and is available for users to download freely without any cost, and modify and use according to their tastes without any tough license obligations.
The positive aspects of Open Source free GPL softwares:
No wonder that GPL licensed products such as Drupal, Wordpress, Joomla, PHPBB and OSCommerce rules the world! They provide truck load of features with absolutely zero cost.