They rely on two different types of motherships as their base of operations, they build the other ships. The classic Skiff comes in regular frigate and hero capital ship versions.
We've taken the basic idea of Arilou ships as your typical UFOs, and ran with that. Today, we already have 2 SC races in the game, the Kohr-Ah and the Arilou. The creator, Danman, also had the intent of adding Star Control races into the game. The mod started by incorporating other mods into it, such as new planet types and visual effects. For those that do not know, there is a mod called 7 Deadly Sins for Sins of a Solar Empire.