Seriously, don't sign a CLA
A contributor license agreement, or CLA, usually (but not always) includes an important clause: a copyright assignment. These agreements are provided by upstream maintainers to contributors to open source software projects, and they demand a signature before the contributor’s work is incorporated into the upstream project. The copyright assignment clause that is usually included serves to offer the upstream maintainers more rights over the contributor’s work than the contributor was offered by upstream, generally in the form of ownership or effective ownership over the contributor’s copyright and the right to license it in any manner they choose in the future, including proprietary distributions.