You would suppose wrong :-)
One of the sample files is a 14k png file.
This is not a JBoss bug. It's just an artifact of the way Oracle has chosen to implement it's JDBC driver.
If you want to store LOBs larger than 4k or so, you must use the OCI driver. It's unavoidable. So, you need to have Oracle client software installed on your JBoss server machine.
Please read the "Map Java byte to database BLOB ?" thread too.
If you're going to post a bug, then post it to Oracle please.