Digital storefronts occasionally give the game away to keep forever:

The Epic Games Store gave away the game as a free limited-time promotion in March 2025. Check their free games section weekly to see if it returns.

Pirated copies will not let you access community features, patches, or official custom challenge modes. If you'd like to proceed with the best option:

Put the game on your wishlist on Steam. It regularly goes on sale during major seasonal events for a fraction of its retail price.