Aisle Seat H,
I think it might be worth a try, but my expectations would be pretty low when it comes to Malev. I've had a fair bit of trouble with them lately (their customer service both at the airport and via the internet leaves a lot to be desired) and I have pretty much closed my Duna Club account and shifted earning to BA. And right now I am boycotting them for travel to Budapest. But if they give the benefit as stated, a free gold card for family member(s) seems like a fantastic deal. The one thing their offer doesn't mention is validity--how long gifted status is good for. But it doesn't specifically exclude other oneworld airlines, so you never know. Again, I would try it since you are flying them anyways and if it works out, great.

My one caveat (I don't know oneworld rules for lounge access very well) is would you be required to credit your miles to Duna club in order to take advantage of the benefits? Probably yes. For you if you're flying a short hop on Malev it's probably worth giving up the miles to upgrade to biz, since all of their flights are short regional flights. But if you're gifting the card to a family member in order for them to use the lounge on a longer flight, I don't think it would be worth it.