[Therenas]

The source is not publicly available, no. It‘s still being actively developed and sold after all. There isn‘t really much of a barrier between engine and 'scripting', it‘s all custom and integrated. The reason there are so few bugs is that there is a ton of effort spent on squashing them! The approach is basically to fix any reported issue if in any way reasonable.

[Zambyte]

> The source is not publicly available, no. It‘s still being actively developed and sold after all.

Those two are definitely not incompatible. Take Karia[0] for example, which is fully Free Software[1].

[0] https://store.steampowered.com/app/1261430/Kandria/

[1] https://github.com/Shirakumo/kandria/blob/master/LICENSE

[Zecc]

Or (while on the subject of Factorio) Mindustry:

[0] https://mindustrygame.github.io/

[BlueTemplar]

Yeah, I wish more games would use this approach, they could for instance have the art assets separate, or do what Factorio does and have matchmaking and the official mod portal to be DRMed. (And/Or give out the source, but not the compiled binaries.)

[lannisterstark]

Factorio is arguably way, way more popular than Kandria, however.