Version 4 is no longer supported.
So what? Were you going to call them? I think the "not supported" means "not commercially supported" and/or "not updated or patched any more since support end date".
Old versions:
https://www.virtualbox.org/wiki/Download_Old_BuildsVirtualBox 5.2 (active maintenance)
VirtualBox 5.1 (active maintenance)
VirtualBox 5.0 (no longer supported, support ended 2017/05)
VirtualBox 4.3 (no longer supported, support ended 2015/12)
VirtualBox 4.2 (no longer supported, support ended 2015/12)
VirtualBox 4.1 (no longer supported, support ended 2015/12)
VirtualBox 4.0 (no longer supported, support ended 2015/12)
They go right back to 4.0.0 if you click "older builds"