If you want to try a multiplayer, game, just post about it. There may be people out there that want to try multiplayer with you, so you can then set a date and time to try it. You can send each other your IP addresses and connect that way (Note: do this via PM for security reasons, don't post your addresses on the forums)
Since there is no combat, war, or system invasions though, there are no victory conditions for you to actually win a multiplayer game, so you'll just have to come up with your own conditions such as colonising the most systems or something.
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