You can buy a DRM-free version directly from Private Division .

Provides a DRM-free version that you can back up and play offline. The "Develop Paper" Context

Occasionally offers games for free as part of their weekly promotions (KSP has been free there in the past).

The search phrase is a common title used by websites that distribute pirated or "cracked" software. While these sites claim to offer the full game for free, they are unofficial and carry significant security risks. Is it safe?

If you want to play Kerbal Space Program safely and support the developers, you should use official storefronts: Often features deep discounts during seasonal sales.

You will not receive official updates, bug fixes (which are frequent in KSP), or access to the Steam Workshop for mods. Legitimate Ways to Play

The .exe or installer files provided can contain hidden scripts that steal personal data or hijack your system.

These sites often redirect you through multiple ad-heavy pages designed to trick you into downloading browser extensions or unwanted software.