In general, the implicit open-source support policy is pretty straightforward: "if you're using an old version, too bad."
Commercial software pretty much works this way too and it's explicit (upgrade or don't call us). Oracle likes to use the term desupported. They have one extra clause where they will often sell you additional support for an old version at such outlandish rates that upgrading doesn't seem so bad by comparison. But when you don't charge anything, it's hard to mirror this model.