Square bans Affero GPL software (squareup.com/us/en/legal/general/pos):
B. Content Restrictions. In addition to the restrictions set forth in these Additional Product Terms, the General Terms and Payment Terms, you will not:
15. use, under any circumstance, any open source software subject to the GNU Affero General Public License v.3, or greater;
The Affero addtion to the Gnu Public License:
If the Program as you received it is intended to interact with users through a computer network and if, in the version you received, any user interacting with the Program was given the opportunity to request transmission to that user of the Program's complete source code, you must not remove that facility from your modified version of the Program or work based on the Program, and must offer an equivalent opportunity for all users interacting with your Program through a computer network to request immediate transmission by HTTP of the complete source code of your modified version or other derivative work.
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