RedSleeve Linux is a 3rd party ARM port of a Linux distribution of a Prominent North American Enterprise Linux Vendor (PNAELV). They object to being referred to by name in the context of clones and ports of their distribution, but if you are aware of CentOS and Scientific Linux, you can probably guess what RedSleeve is based on.
RedSleeve is different from CentOS and Scientific Linux in that it isn’t a mere clone of the upstream distribution it is based on – it is a port to a new platform, since the upstream distribution does not include a version for ARM.
The reason RedSleeve was created is because ARM is making inroads into mainstream computing, and although Fedora has supported ARM for a while, it is a bleeding edge distribution that puts the emphasis on keeping up with the latest developments, rather than long term support and stability. This was not an acceptable solution for the people behind this project, so we set out to instead port a distribution that puts more emphasis on long term stability and support.