There’s one other clause that you’re missing: you may not further restrict the redistribution of GNU GPLed software (either source or binary). So D-Link may restrict distribution to “on request” by “people who bought our hardware”, but they cannot stop one or more of those people from redistributing the software obtained thereby.

That, plus the fact that if you incorporate any GNU GPLed software in your own software your own derivative software must be licensable under the GNU GPL, or be more liberally licensed, makes for the uncomfortable discussions with lawyers about use of GNU GPLed software in any company.