What do you consider "not legitimate?" If they're trying to get to some secured code and do wholesale copyright infringement then that's obviously wrong. I don't see anything wrong with reverse engineering a competitor's product, though, to see how it ticks or to establish what kind of functionality it might have.
first, I do not see why you need more than using the product to determine "what kind of functionality it might have".
second, I have 'disassembled' when a factory burned and the source was lost and found that the effort to disassemble is way more than the effort to recereate.

Thus, in my opinion, there is no value to 'disassembling' and thus no value to reading a given object code if you are not going to use it outright. Thus, were I to show dancing pigs on my signs, my competitor would be better off starting from scratch that trying to 'unlock' my code.

Is there anything dishonest about taking a look at the competitors product? absolutely not, is there anything dishonest by copying a routine 'unlocked' from the competitors code, absolutely. I do agree that the line between "taking a look" and "copying" can be fuzzy. As an example, if I see a competitor using some 'unusual' 485 transciever, I will look at the datasheet for the transceiver and try to determine the reason for the choice and If I see that being a better choice than mine, I may switch. However, I would never copy the code driving it.

Erik