You may want to wait...
MYOB is overhauling their 90's style application (netbios/etc), moving it to .net framework with an API (they said it would be done Q2 2009, moved to Q2 2010).
They have non complaint SQL syntax (insert/select), yes that's right only two keywords... (the idea is if you screw up the query, say to an invoice, you have to write a insert into the credit table)
Unfortunately, read/write functionality doesn't come with the MYOB licence. If I can remember correctly it was Read for AUD$250 one time and AUD$800yr for write permissions. Most companies can afford as it cuts down on labor.
The ODBC driver hard to use, because it executes the MYOB application and leaves it in the background. (you may want to create your own rest service to query)