A CLA is what legally allowed Oracle to release the once copyleft OpenSolaris under a closed source license, including code contributed outside of the previous owner company, Sun. CLA is a tool for companies to change the deal after the deal.

There's a famous talk about this, which resulted in many us referring to Oracle and its billionaire CEO as the "lawn mower."

https://www.youtube.com/watch?v=-zRN7XLCRhc&t=2482s