Bus is a demonic entity that exists only within Outside. Bus has been called many names throughout human history, such as "The Back" and "Late". Bus, while indifferent to the denizens of Outside, is actively hostile to developers of Free Software. The mechanisms that allow it to be aware of who is a developer and who is not are unclear. To date, no one has been able to capture Bus to analyze it's anatomy. Various traps have been set up to capture Bus, but Bus, consciously or not, has been at least half an hour late to arrive at all of these traps.
Bus commonly will strike developers by ramming them, usually killing them instantly. This causes all projects the developer was working on to vanish into a magnificent storm of glowing particles that ascend towards the heavens where the deceased developer's soul rests. After which, all of their projects are gone from our earthly realm, never to be seen again.
Due to obvious reasons, Bus has some relationship or affinity for Windows users. It is unknown if one is capable of controlling the other, or if they simply have a mutual relationship. Bus is considered a deity in Windows user culture.
It is currently believed Bus has some relationship with Kniferat. The status of this relationship is unknown.