The Online Recruitment System for Economic Experiments is `Citeware' and is available under a proprietary open source license. ORSEE is free of charge. However, researchers using the software to organize their experiments must acknowledge the software's use by an appropriate citation of this article.
The license in full text:
Copyright (c) 2003-2020 Ben Greiner (email@example.com). Author(s): Ben Greiner ORSEE is citeware. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. The use of derivative works is restricted in the following way in accordance with standard academic citation practices: Any academic report, publication, or other academic disclosure of results obtained with the use of this software will acknowledge the software's use by an appropriate citation of the following publication (or an updated version): Ben Greiner (2015), Subject Pool Recruitment Procedures: Organizing Experiments with ORSEE, Journal of the Economic Science Association 1. Forthcoming. http://link.springer.com/article/10.1007/s40881-015-0004-4 2. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 3. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 4. The names of the author(s) and/or the software must not be used to endorse or promote products derived from this software without prior written permission. 5. Products derived from this software may not be called "ORSEE", nor may "ORSEE" appear in their name, without prior written permission of the author(s). THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.