No Registry Changes: It doesn't modify the Windows Registry or system folders.
Autodesk provides DWG TrueView (for Windows). While not a full AutoCAD, it is a free, official viewer that can be made portable with some effort. You can download the installer, extract it using 7-Zip, and run DWGView.exe directly from a USB drive without admin rights. Portable.Autodesk.AutoCAD.2010
Absolute no. On every level.