Give it away or recycle

As for giving it away, make sure the potential recipient knows what they are getting limitation-wise.  While the NV+ was a great starter NAS in it's day, it now comes with so much limitation and baggage that it's a struggle for beginners.  It does have some value, though.  Somebody who owns an NV+ may want it as a spare since data recovery from a failed one is easiest  by just moving the drives to another unit.  The drive trays, especially if they are the newer square-button instead of the older round-button ones, have value because many ReadyNAS are sold without them.  The power supply can also be used in other models, so has value.