Once you extract your data from MYOB, consider dropping it into SQL-Ledger, a GAAP compliant accounting package written in perl which uses postgres as its backend. The SQL-Ledger site has a page on converting from one accounting program to another, at:

http://www.sql-ledger.org/cgi-bin/nav.pl?page=misc/conversions.html&title=Conversions

It does not list MYOB, but if you can convert to Quicken or GnuCash, there is a pathway to get you all the way home to a perl based application.

Good luck.