The way you get a REPL circa mzscheme 4 is to pass -i, but
-i, --repl : Run interactive read-eval-print loop; implies -v
-v, --version : Show version
and they changed the -m flag to mean
-m, --main : Call `main' with command-line arguments, print results
So, using -i will still display the banner, and there doesn't seem to be an option to mute it.
$ mzscheme -if as.scm
Welcome to MzScheme v4.1.5 [3m], Copyright (c) 2004-2009 PLT Scheme Inc.
Use (quit) to quit, (tl) to return here after an interrupt.
arc> ^Cuser break
=== context ===
~/arc/ac.scm:1141:4
> (tl)
Use (quit) to quit, (tl) to return here after an interrupt.
arc>
