We know that Matrix, for whatever reason, does not want to bring Distant Worlds to Steam. That needs to be accepted (regardless of what one may think of the decision) and move on from it.
The reasons are fairly obvious, I think. The pricing on Steam is tremendously lower and there's always a bunch of games on sale, which means DW would look prohibitively expensive by comparison and possibly generate negative PR. Nobody would buy an "old" 2D game for $40 or more and DW is really at its finest when it does have all the expansions included. In other words, the price would have to be dropped a whole lot and after Valve's cut the income per unit sold would be tiny.
With this in mind, looking at possible strategies for marketing and the one that comes to mind for me is a referral program. A good referral program works extremely well with a product that is well received and people want more of. Most strategy gamers know other strategy gamers who know more strategy gamers who know people who might want to try something new who know etc..
A good referral program encourages people to spread the word via word of mouth and increases sales dramatically if, and only if, the program rewards the legwork with something that is desired. In this case Distant Worlds - Universe. A simple program of $10 USD off per referral (who buys) that is open to everyone (regardless if they currently own the game or not) might work.
Two words. PONZI SCHEME!!!
I'm personally not a fan of referral programs and similar schemes where users get a financial incentive to convince other people to buy something. It results in exaggerated recommendations and unhappy buyers, who will then try to get some of their money back by talking other people to buy the game. Good for Matrix and Code Force, but also something that ought to earn them a whole stack of dark side points.
Depending on how much energy that the guys at Matrix wanted to put into it (I'd guess minimal at best to keep in line with their current methods) they could maintain a "leaderboard" of the top referrals and update it as it goes up. This would ignite the competitive spirit of a portion of the people involved.
I'm sorry, man, but this is even worse. Now we're making a sport out of paying customers competing to make other people buy a game regardless of whether the game actually appeals to those other people. I, for one, would really, really, *really* like to see this not happening. Just my personal opinion, mind you.
So, what happens if someone refers enough people (who buy) to get the game for free? Should it stop there? I don't think so - allow them to build up to another free copy of the game or more. Then they could give it away.
Why, hello there total Ponzi Scheme. Can you imagine just how terrible this could get in terms of PR? Paying gamers to use whatever means to get other gamers to buy the game? You know, if Matrix goes this path then I'm not sure I'll buy Universe. I'm just not very good at going dark side.