Okay, here is a proposal.
To support custom licenses, we can extend the basic syntax of SPDX with expressions that look like:
license: unusual/<id>
Those licenses must be carried by the snap under meta/license/<id>.txt, in pure text format. The ID must match “[a-zA-Z0-9-.]+”.
Here is some of the rationale behind the proposal:
- That representation allows multiple licenses to be conveyed, using richer SPDX expressions.
- Something unusual means not used often. If it was usual, SPDX should cover with a first class identifier.
- Something unusual tends to be an eye-opener.
- Publishers will naturally prefer not to label their license as unusual, if possible.
- At the same time, “unusual” is not “bad” either. It simply means it must be looked into.
- It blurs the line between proprietary and unknown open source licenses. This reflects reality: if the license has custom unknown terms that weren’t vetoed by a recognized entity, it may be a trap to account it as free software.
- It gives a choice for proprietary software to express their terms. People often consider “proprietary” as simply “not free software”, but both free software and proprietary software have variations in their licensing terms.
Then, taking this chance, we’ve agreed to label missing licenses as:
license: unknown
Per the plan described in the respective topic, at some point in the near future snaps not defining a license will stop being accepted by the store. Before that happens we’ll wait some time after the feature is fully implemented so everybody has a chance to amend their metadata.