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

I doubt it. It might be problematic if you plan on shipping your product with that blaster though but that's more to do with the blaster than what you have connected it to.

This goes without saying, don't expect Altera to support you if the blaster doesn't work properly. For something important like on-chip debug getting the real thing might be a good investment rather than debugging with a potentially flaky programming cable.