While the base game should be downloaded officially, many community-made mods (buses, maps, and skins) are hosted on external sites:
If the search is driven by budget concerns, here is how to get the game legally for a similar price—without the viruses. Omsi 2 - Download Pc Mediafire
Use WinRAR or 7-Zip to unpack the folder to your desktop. Run the Installer: Open the Setup.exe file. While the base game should be downloaded officially,