CLAs are very misunderstood in the software industry. Every open source project
should make its contributors sign CLAs, and you should be wary of using one that doesn't. Why? Because any single contributor can claim at any point in the future that the project is using their code illegally, and that you/your company should pay them for using their proprietary IP for all of these years. Can you prove that you audited every single line in the project you used and were sure of its copyright status? A CLA ensures exactly that. There's a reason why Linux Foundation, Apache, CNCF, Mozilla, heck even FSF all have strict CLA requirements.
Relicensing is a completely separate conversation, and there are plenty of open source CLAs which don't have that provision.