@maija Merely because something is mostly source-available (aside from a few "optional" parts) doesn't mean it's not proprietary.

The classic example of this is source code published without a license - all you can legally do is look at it - you can't share it or modify it and in some jurisdictions you can't even compile it, as compilation is seen to be modification.

The "SSPL" is proprietary, as it's specifically designed to have unreasonable terms that are impossible to comply with, so MongoDB can go and extort people and businesses that use the software by demanding payments for an exception (not sure if it's one off or ongoing, but I figure it's the latter) and the receiving end has to either pay or stop using the software.

Previously, MongoDB tried this extortion method with the AGPLv3, but it often failed as a lot of targets just compiled with the AGPLv3, so they took the AGPLv3 and modified it into a new license that is proprietary and figured rightly that people would assume that the resulting modification was a free license.