Different licenses require different criteria. For instance, under the GNU General Public License (GPL) published by the Free Software Foundation (FSF) for licensing free software, any work based on the program or any other derivative work must be licensed as a whole at no charge at all to all third parties under the terms of the GNU GPL, whereas an Apache License does not require derivative works to be open source. You can add your own copyright statement to modifications of a source code under Apache License and provide additional or different license terms and conditions for use, reproduction, or distribution of your modifications, or for any derivative works as a whole, provided your use, reproduction, and distribution of the work otherwise complies with conditions of the Apache License. Similarly, there is no requirement that any derivative work created under an Academic Free License (AFL) or a Berkeley Software Distribution (BSD) License, should be distributed at all, or for free if distributed. Further, any derivative work need not be free and one can charge for it as you would for proprietary software.

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