Here are diffs for mush-7.2.5; they work for NetBSD 1.0 and
the May 15th freeze for me.  The added object file is regex.o,
which you may have source for.  If not, I used the Gnu version
0.12, I think.  I have tried a few times to compile the newest
patches which are called 7.2.6-alpha, but no luck on NetBSD so
far.  Any one else working on this?

*** makefile	Fri Feb 10 14:29:38 1995
--- makefile.bsd	Fri Oct 30 14:55:06 1992
***************
*** 12,18 ****
        signals.o setopts.o msgs.o pick.o sort.o expr.o strings.o \
        folders.o dates.o loop.o viewopts.o curses.o curs_io.o bind.o \
        lock.o macros.o options.o addrs.o malloc.o glob.o command2.o \
!       pop.o pmush.o xcreat.o regex.o
  
  HELP_FILES= README README-7.0 README-7.1 README-7.2.0 README-7.2.2 \
  	README-7.2.4 mush.1 cmd_help Mushrc Mailrc Gnurc \
--- 12,18 ----
        signals.o setopts.o msgs.o pick.o sort.o expr.o strings.o \
        folders.o dates.o loop.o viewopts.o curses.o curs_io.o bind.o \
        lock.o macros.o options.o addrs.o malloc.o glob.o command2.o \
!       pop.o pmush.o xcreat.o
  
  HELP_FILES= README README-7.0 README-7.1 README-7.2.0 README-7.2.2 \
  	README-7.2.4 mush.1 cmd_help Mushrc Mailrc Gnurc \
***************
*** 22,28 ****
  
  # See the README for changes needed to compile under Ultrix.
  # In particular, you may need -DSIGRET=void and/or -ltermcap.
! CFLAGS= -O -DCURSES -DBSD -DNETBSD -DSIGRET=void
  LDFLAGS=
  LINTFLAGS= -bxah -Dlint -DCURSES -DBSD
  LIBS= -lcurses -ltermlib
--- 22,28 ----
  
  # See the README for changes needed to compile under Ultrix.
  # In particular, you may need -DSIGRET=void and/or -ltermcap.
! CFLAGS= -O -DCURSES -DBSD
  LDFLAGS=
  LINTFLAGS= -bxah -Dlint -DCURSES -DBSD
  LIBS= -lcurses -ltermlib
*** mush.h.df	Fri Oct 30 14:55:40 1992
--- mush.h	Sun Aug 27 21:52:55 1995
***************
*** 211,216 ****
--- 211,220 ----
  #endif /* CURSES */
  #endif /* SYSV && USG || AIX */
  
+ #ifdef NETBSD
+ #define USE_OLD_TTY
+ #endif
+ 
  #if !defined(USG) && !defined(AIX)
  #ifndef CURSES
  /* if curses is not defined, simulate the same tty based macros */
***************
*** 228,234 ****
--- 232,242 ----
  #endif /* ~USG */
  
  /* With all that out of the way, we can now declare our tty type */
+ #ifndef NETBSD
  SGTTY _tty;
+ #else
+ static struct sgttyb _tty;
+ #endif
  
  extern char
      del_line,		/* tty delete line character */
***************
*** 477,483 ****
--- 485,493 ----
      *popen();		/* this should be in stdio.h */
  
  extern char
+ #ifndef NETBSD
      *sys_errlist[],    /* system's list of global error messages */
+ #endif
      **environ;		/* user's environment variables */
  
  extern int errno;	/* global system error number */