License 　－　About 9arrows' License

9Arrows is open source software in accordance with GNU GPL License v3. GPLv3.  GPLv3 assumes the opening of source code to the public to be a leading principle; it allows freedom of re-distribution and modification.  In the case of modification or re-distribution, we ask that you too conform to this license.  (Please refrain from hiding improved source code.  If you would prefer not to make updated code publicly available, please inquire first.)

Licensing regulation: English

http://www.gnu.org/copyleft/gpl.html