> The whole point of open source licensing is to prevent future releases from being under more restrictive licenses.
That a point of copyleft licenses. It's not a point of permissive licenses. Providing a certain degree of freedom to the direct licensee is the common shared point of open source licenses, permissive and copyleft.
There is no canonical set of purposes behind any license, copyleft or permissive. The license drafter had their own goals in mind, but their terms get repurposed by others.
Even very popular permissive licenses have been written with contribution front-and-center in mind. See, for example, the contribution-related terms of Apache 2. The definition of contribution. The built-in CLA. The compromise on scope of the patent grant.
Fair point on the semantic vagueness of "open source", I'll exercise more caution. However, I think it was clear in context what category of licenses I and the main conversational thread are referencing.
That a point of copyleft licenses. It's not a point of permissive licenses. Providing a certain degree of freedom to the direct licensee is the common shared point of open source licenses, permissive and copyleft.