Is there any law problem when our company use a 3rd-party usb-blaster to update the p

We use Terasic and Altera USB-Blasters too, and both are fine (apart from the Altera cable is now broken due to overuse!). The Terasic blaster is 1/4 price of the Altera one though, so well worth it. I think the only time you might want to make sure you are using an Altera programmer is if you are programming security encryption keys in something like a Stratix II part as that uses non-standard voltages etc. But if you do that Altera write-off most of your guarantees anyway......