

So GPU is still used, but it doesn't do anything smart. When we say that game "doesn't use GPU", we mean that it uses CPU (central processor) to calculate the color of all pixels that need to be displayed, and then feeds that result to GPU (which shows it on the screen). But Starbound doesn't use GPU, so having vsync means "your CPU needs to do more work". Why it helps: 99% of games don't suffer from vsync being enabled (in fact, it's better for them), because vsync is normally done by GPU. Edit it, replacing the line "vsync" : true, (which is slow) with "vsync" : false, (which is faster).

It also doesn't use the GPU (all graphics are calculated by CPU). It only uses 1 CPU core for server (in singleplayer too), and only 1 CPU core for client. Starbound (by itself, even without any mods) is very poorly optimized.
