Open source is a term that loosely describes software that is licensed under terms that allow the user of the software to look at the source code and modify it, and to distribute the modifications. Beyond these general characteristics, open source licenses vary widely in their requirements. Some open source licenses (for example, the BSD license) allow modifications to be kept proprietary; some (such as the General Public License, or GPL) require that the source code for any modifications also be distributed and modifiable by users. Open source licenses generally allow the distributor to charge a distribution fee. A wide range of licenses could theoretically be called "open source," so the Open Source Initiative (OSI) provides a certification mark for licenses that meet its definition of "Open Source." OSI has approved the most commonly used open source licenses. More information about OSI and approved licenses are available at https://opensource.org/licenses. If you are developing some software that you think you would like to release under an open source license, the OTL can help you find the best distribution model and identify in advance any potential conflicts and restrictions resulting from the use of such a model (for example, encumbrances created by sponsored research agreements or issues created by the requirements of the license you would like to use) in advance.