The name for the full-screen environment in AppleRhapsody that enabled you to run previous editions of the Mac OS side-by-side with the AppleRhapsody desktop. This was the predecessor of Classic in MacOSX.
“Transparent Blue Box” is not an nickname for Aqua, but refers to Blue Boxes (including Classic) that interleave their windows as peers to those of native apps.
The Blue Box was put together by NuKernel refugees working with the MAE group. MAE was a proto-blue-box for open systems that was essentially A/UX 3.0.1 running emulated on Solaris, HPUX.