Autodesk has never released an official portable version of AutoCAD 2010 or any other version. The only official portable Autodesk products are certain mobile viewing apps (like AutoCAD 360) or specialized tools like "DWG TrueView," which is a free viewer, not a full CAD editor.
NanoCAD has a free version that reads/writes DWG files natively. It is not lightweight but is 100% legal and free for commercial and personal use. Download Autocad Portable 2010 Free
Released in 2009, AutoCAD 2010 (internally known as "Gator") introduced several key features that revolutionized computer-aided design: Autodesk has never released an official portable version