Scaleform GFx

The Skyrim UI is built on Adobe Flash and the ActionScript 2.0 scripting language.

AutoDesk Scaleform is a middleware that lets developers integrate a custom Flash/AS implementation into their engine/game that is optimized for games on PC/Console/Mobile/etc. Yea the same company behind AutoCAD and 3DS Max.

Adobe Flash CS6 is the last IDE edition capable of editing the Skyrim UI. Versions after that have had the AS2 functionality gutted.

Flash is a decent tech but its days as a web technology are over. It is great for interactive animations though.