I.e., on any of the supported platforms, does squeak use "native" windows for its windows, or do all platforms render into a window like is currently done on the BeOS?
I think that most platforms do it the same way (I can't really speak for *all* platforms) that is, copy the Squeak Display object into the hosts Squeak window. There are slight differences in the way the different ports deal with byte reversal (e.g., on Win32 this is done inplace, once before copying the Display object into the window and once after this has been done) or whether a host bitmap is needed for Display. But besides that your exactly on the right trail.
Andreas