You might like to check out MenuetOS/KolibriOS and the old QNX demo disk.
Both provide GUIs and rudimentary Web browsers. QNX was full POSIX, too, although the demo disk didn't include a terminal.
Both provide GUIs and rudimentary Web browsers. QNX was full POSIX, too, although the demo disk didn't include a terminal.
You try fitting all that plus a GUI those constraints.
What's amazing is that it had the features it had and that it worked at all.