Comment by tzs

They aren't responsible for ensuring that others can install it.

That part of GPLv3, commonly called the "anti-Tivoization" clause, only applies if you "convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized)".

This was narrowly written to only cover situations like Tivo, which was a hardware vendor locking down GPL code on the hardware they sold.