Free software, freedom-respecting software, software libre, or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute the software and any adapted versions. The right to study and modify software entails access to its source code. For computer programs that are covered by copyright law, this is achieved with a software license by which the author grants users the aforementioned freedom. Software that is not covered by copyright law, such as software in the public domain, is free if the source code is in the public domain, or otherwise available without restrictions. Other legal and technical aspects, such as software patents and digital rights management may restrict users in exercising their rights, and thus prevent software from being free. Free software may be developed collaboratively by volunteer computer programmers or by corporations; as part of a commercial, for-profit activity or not.