"The LLVM project does not require copyright assignments, which means that the copyright for the code in the project is held by its respective contributors who have each agreed to release their contributed code under the terms of the LLVM License.
An implication of this is that the LLVM license is unlikely to ever change: changing it would require tracking down all the contributors to LLVM and getting them to agree that a license change is acceptable for their contribution. Since there are no plans to change the license, this is not a cause for concern.
As a contributor to the project, this means that you (or your company) retain ownership of the code you contribute, that it cannot be used in a way that contradicts the license (which is a liberal BSD-style license), and that the license for your contributions won’t change without your approval in the future."
OOPS.