Unlike most modern games, BeamNG.drive offers a DRM-free version via the Humble Store. If you hate Steam, you can buy the game, download the installer, and save it to your own external hard drive. This is the real portable version, but it is legal and official.
The Risks of Downloading BeamNG.drive via Mediafire: Why Official Channels Matter
Files are often compressed poorly, leading to missing archives and installation errors.
Unlike some hosting sites, Mediafire offers relatively fast download speeds for free users.