I'm not sure what the issues with lesstif installation are.
Normally, I have a machine with real Motif handy I can just copy off
(this is how I think I re-installed lesstif after the lesstif Makefile
installed it!) Actually, my Xm directory is in /usr/local/include also,
so I'm not sure why the compiler can't find the files. Try addinf
/usr/local/include to the xinc variable in the Makefile.
     I have some modified makefiles and source files you could just
untar into the Mosaic-src directory. You would then type make nbd and
the whole thing would just compile with no hassle. This, of course, is
no fun :) I could mail these to you. One day I hope to have an internet
connection (a real one) and my own anon ftp server, etc., but I'm not
there yet! Is there a place I could put them for all interested macbsd
users? Should I even bother? Mailing my changes to NCSA would probably
get a good laugh. They'll release 2.7b5 just on account of me. They
could post a binary though...
     For 2.7b5 there are only about 3 changes you need to make to the
Makefile.bsdi makefile in the makefiles directory (tell it where the png
and jpeg dirs are, then cut out -lipc in syslibs. Maybe you have to
specify -DMOTIF1_2 somewhere, I don't remember.) Not counting the source
changes necessary for a compile, this method might actually be
preferable to using configure. Plus, if you get good at Makefiles,
mMosaic (I just compiled mMosaic 3.011) is a logical next step to
compile. With mMosaic you finally get table support and the center tag
works. You can finally view the NetBSD home page properly! mMosaic is,
however, probably buggier than Mosaic 2.7b5 in some aspects. For the
interested, mMosaic is available at
ftp://ftp.digital.com/pub/X11/contrib/applications/mMosaic-3.0.11.tar.gz.

Share and enjoy,
-Steven