You would say "back in XXXX" to emphasize that it happened some time in the past. Otherwise there is no difference in meaning.

I graduated high school in 1984

I graduated high school back in 1984.

You can also say "way back in" to emphasize that it happened a (relatively) long time ago, as if it was ancient history.

I graduated high school way back in 1984.

So with regard to your example, saying "EVE Online launched back in 2003" emphasizes that the game has been around for quite a while. This will usually be relevant to some other point mentioned before or after -- for example that, as a result, the game is polished, or has an established player base, or that the developers are committed, and so on.

You would say "back in XXXX" to emphasize that it happened some time in the past. Otherwise there is no difference in meaning.

I graduated high school in 1984

I graduated high school back in 1984.

You can also say "way back in" to emphasize that it happened a (relatively) long time ago, as if it was ancient history.

I graduated high school way back in 1984.

So with regard to your example: saying "EVE Online launched back in 2003" emphasizes that the game has been around for quite a while. I expect this is relevant to some other point mentioned in the article -- for example that, as a result, the game is polished, or has an established player base, or that the developers are committed, or something similar.