Contributor Agreements, also known as Contributor License Agreements (CLA), are increasingly being adopted by open source projects. This article explains the purpose of these Contributor Agreements.
When a contribution is made to an open source project, there is an implicit assumption (and sometimes explicit consent) that the contribution (code, translation, artwork, etc) may be incorporated into the project and distributed under the license the project is using. However, many conditions of the contribution are not explicitly called out. The purpose of Contributor Agreements is to make the terms under which contributions are made explicit, thereby protecting the project, the users of the software and often also the contributors.