Generally sustainable software licenses are divided in two main distinct parts:
1) Free access to the source code for research, test and development purposes
2) Rights of using the software for internal deployment or for commercial use
1) The first part of the software license lets you access to the full source code free of charge, at any time, anywhere. This part also stipulates what developers can or can not do with the source (e.g. viral effect of royalties on derived work ). This first agreement is usually limited to research and development purposes only.
2) The second part of the license (or as a separate optional agreement) stipulates your rights to use the software for any other valuable deployment use (number of servers, number of users, number of devices,...) and mentions the overall cost of your license as a customer. Any sustainable programs shall allow you to be fairly rewarded for your contribution and should for example allow you to pay part or whole of your license fee in cash or in kind. An optional addendum can then be fulfilled in order to allow both parties to agree on a counterpart in kind that will provide a full or partial discount on the total cost of your license fee. This section also usually cover the distribution requirement in source code or in executable version.
List of compliant sustainable software licenses: