It depends on the dried seaweed. Kombu (dried kelp) comes in several different varieties that are carefully harvested in different areas. Most things labelled "dried seaweed" are completely edible, but as far as I know(? I'll be happy to take correction) kombu is never eaten. I certainly don't fancy it - a bit too much of an iodine-rush.
However, that said, I harvest my own fresh kelp (here in Puget Sound, after storms) and sun-dry it. I tried making dashi using fresh kelp ...
NO. But dried, it's great and even develops the proper salty look. Most important to this Scotsman, the price is right