Another interesting clause that is expired by the copyleft sunset clause is the ability
for recipients to enforce the license. To quote an excerpt from section 5
`
Each direct and indirect recipient of the Covered Work from You is an
intended third-party beneficiary of this License solely as to this
section 5, with the right to enforce its terms.
'
This clause gives individual recipients of the software the ability to claim their rights
to use, modify, reinstall, and redistribute the software.
I cannot understand why would user rights be made temporarily enforceable.
In case of proprietary copyright, it makes total sense to limit the period in which the
author is allowed to be greedy, but not so with copyleft.
It makes more sense to make proprietary software as well as permissively licensed software
fall back to Copyleft after a certain period of time. Meaning, that one who does
incorporate permissively licensed software within a proprietary software product, could
only do it for a period of time, after which they would have to release the source code of
the entire work including the proprietary parts under a perpetual copyleft license that
give the rights back to the users in a permanent way such that any further
proprietarization of the software is not possible.