How much does winaprs and aprsair cost to register???

I want to display airline flights that transmit on 131 Mhz for the
purpose of propagation monitoring only and don't need any of the
packet functions.

So, I'm trying to decide whether to get aprs/aprsair or whether to
just get acarsd (which is free, but doesn't require a tnc, but has
less options for mapping).

M