Exercism.io is free and Open Source.
The website prototype is written in Ruby using the Sinatra web framework. It is licensed under the GNU Affero General Public License.
The command-line client is written in Go, and distributed under the MIT license.
The exercises in the various languages are also released under the MIT license.
An overwhelmingly large number of people have contributed to the codebase.
An even larger number of people have contributed through participation; by completing exercises and participating in the discussions about code.
Individual exercise submissions are owned by their author, and may or may not be distributed under an open source license.