MarcEdit isn't open source.  If you need open source and don't mind 
java marc4j handles round trip conversion.
"Support for data conversions from MARC-8 ANSEL, ISO5426 or ISO6937 to 
UCS/Unicode and back."
http://marc4j.tigris.org/


Quoting Marc Chantreux <[log in to unmask]>:

> hello,
>
> On Tue, Oct 23, 2012 at 01:31:39PM +0000, Joseph Montibello wrote:
>> Hi,
>>
>> There's a perl module that should do this:
>> http://perldoc.koha-community.org/v3.00.00-stableRC1/C4/Charset.html
>
> i really don't plan to install koha but i can steal the C4::Charset
> stuff to get it out of koha.
>
> AFAIR, there is no way to come back from UTF8 to iso5426. am i right ?
>
>> MarcEdit lists a recent enhancement that supports iso5426 as well.
>> http://people.oregonstate.edu/~reeset/marcedit/html/index.php
>
> oh! is this open source? i has no success in searching for a source
> repository.
>
> regards
>
> --
> Marc Chantreux
> Direction Informatique
> http://unistra.fr
>