rustc-rayon is a fork of the Rayon crate. It adds a few "in progress" features that rustc is using, mostly around deadlock detection. These features are not stable and should not be used by others -- though they may find their way into rayon proper at some point. In general, if you are not rustc, you should be using the real rayon crate, not rustc-rayon. =)
rustc-rayon is a fork of rayon. rayon is distributed under the terms of both the MIT license and the Apache License (Version 2.0). See LICENSE-APACHE and LICENSE-MIT for details. Opening a pull requests is assumed to signal agreement with these licensing terms.