Tar-mode is a JED interface to GNU tar.  It was written by Paul Boekholt.
To install, place tar.sl, tarlib.sl and tarhook.sl
in your jed_library_path and add

require("tarhook");
to .jedrc. 
If you want want tar archives to be opened automatically in tar-mode, add

add_to_hook("_jed_find_file_before_hooks", &check_for_tar_hook);
otherwise add

autoload("tar", "tar.sl");
and if you prefer dired- to MC-bindings add

variable FileList_KeyBindings = "dired";

The read-only argument to tar() needs some explanation.

Users who open a tar-archive with ^X ^F might assume that changes do not
become permanent until they do ^X ^S.  This is the way Emacs' tar-mode works
but not JED's tar-mode.  To protect these users, the check_for_tar_hook
always opens tar archives in read-only mode.

Users who open a tar archive from filelist.sl may be assumed to be assuming
a filemanager model, so it's opened read-write (if the tar is not
compressed; GNU tar can't delete from a compressed archive).

Users who open archives with M-x tar are assumed to be grown-ups.

If you open a tar with JED from within a MUA, it should be done read-only,
so if you have added the tarhook you can simply add
application/x-gtar;   jed '%s';
application/x-tar-gz; jed '%s';
to your .mailcap, otherwise try something like
application/x-gtar;   jed -f 'tar("%s", 1)';
application/x-tar-gz; jed -f 'tar("%s", 1)';

If you want to open tar archives read-write from e.g. Midnight Commander (MC
has it's own tar viewer, but it's read-only) open HOME/.mc/bindings, look
for the entry

# .tar
shell/.tar
	Open=%cd %p#utar
	Extract=tar xf %f
	...
	
 and add
 	Edit=jed -f 'tar("%f", 0)'