Why would Dapol's instructions refer to it using the Lais product number if Lais were pirating Dapol's product.
Theres no if's, buts or maybes about it. The Imperium 1 and 2 are LaisDCC decoders with the shrinkwrap removed, CV7 changed to Dapol (I think) and stuck in a Dapol box.
Never used any of the other Imperium decoders so can't comment on them.
Now maybe Dapol didn't exactly rock up to Lais and say "We want to rebadge your decoders, price please" and really just commissioned a factory in China to make decoders for them and said factory just bought them from Lais. Nobody will ever know for sure.