even with other FOSS licenses, the copyright holder can re-license the project
Re-licensing the project means future releases go out under a new license. Past releases remain as they are, because they are non-revokable (unless breached; but let’s be real, if you breach an agreement you should stop benefiting from it).
As a user, or a developer?
Both. A user that doesn’t care about licensing is typically called a pirate.