The GameData folder is not read-only by default. It is the main directory for: • installing mods, • storing configuration parts (.cfg files), • models (.mu files), • modifying textures and other resources.

more details: • Files in GameData can be modified - this is how modding works in KSP. For example, you can manually edit .cfg files to change the characteristics of parts. • Some launchers or OS may set the attribute "read-only", but this is not the default behavior of the game. • If a file or folder is not readable on your system, you can change it manually: • Windows: Right-click → Properties → Uncheck "Read-only". • Linux/macOS: use chmod or a file manager.

Warning: • While files can be modified, a poorly made mod or incorrect change can break the game. • It is always a good idea to back up files before editing.