Forewarning: I have yet to actually play Pulsar.
It’s certainly in the same niche as Artemis, but I don’t see it acting as a full replacement. Artemis, as it says in the title, is a Spaceship Bridge Simulator where everyone controls parts of the ship directly, and can support up to eight ships for Coordinated Fleet Action™. It also has a singular focus on killing aliens until they are dead.
Pulsar, on the other hand, has (what looks to be) a smaller max amount of players controlling avatars that control a single ship. The emphasis here seems to be more on exploration and discovery, with combat still around to spice things up. It reminds me of a much smaller version of what the persistent universe part of Star Citizen promises to be. While i’m very much looking forward to that, I don’t see SC replacing Artemis either.
Artemis can also be a very immersive LAN experience, while I can’t see Pulsar pulling off the same thing.
I’ll admit, though, Pulsar looks rather interesting. One of the few I’d actually consider getting in it’s un-finished form. So if anyone else wants to check it out as well, you know where to find me.