As with frob, I'm not staff here -- the mod tag just means I volunteer to clean up spam and very occasionally shut down trolling... I'm really just another user on the forums here.
I'm not sure what kind of "working together" you're after? You should probably refine that line of thought into some kind of concrete proposal first.
Basically, there's a successful website (from what I can tell from the outside, running GD.Net isn't much of a profitable business, so successful just means, "long existing and not bankrupt") and a 3rd party has gone and bought an extremely similar domain name and then approached said business with a vague request to work together. I'm not surprised that this is a conversation that 'sort of trailed off'; there's not much substance to it.
I mean, if I emailed Coca Cola saying "Hey, I just bought cokacola.com, do you want to work together with me?", I wouldn't even expect a reply...
If I was GD.Net or Coke, and someone gave me these alternate URLs, I'd take them and just set them up as redirects to my real URL.
On the other hand, if someone with these alternate URLs said, "let's work together", I'd wait for their proposal, because all I've thought of is using their URL as a redirect...
But if as you suggest I should instead be looking at this as a business thing
You've invested a lot money (apparently enough to pay for an overseas holiday for two) in acquiring a domain name -- that's either a business decision, or an investment into an extremely expensive hobby.
I can only assume you'll want that investment returned over time? The common way to do so is to make great site that people want to visit and then putting ads on it. Hopefully the ad income will be greater than your hosting costs so that there's a small amount left over that will gradually pay off your initial investment...
To be frank, you probably should've thought a bit about your business plan before making that initial huge investment