SuperCollider is copyright © James McCartney and many other contributors.
SuperCollider is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.
Some further notes:
SuperCollider was originally published under the terms of version 2 or later of the GPL, but the application now includes some GPL3-licensed code. If you have a need specifically for GPL2 compatibility then it is possible to recompile SuperCollider from source without the GPL3 elements.
SuperCollider's help documentation is published under a Creative Commons license.