Free Software Licence
Some licence agreements grant considerably more rights than most End User Licence Agreements (EULA) provide. A free software licence grants the right to modify and redistribute the licensed software, both of which would ordinarily be forbidden by copyright law. In some cases, these rights are accompanied by copyleft restrictions, adding requirements to redistribution. For example, some free software licenses require the distribution of complete source code along with the software or some specific form of attribution of authorship.