As far as I know, the Bung/Visoly/EMS linkers are all designed around an EPP-based protocol. Strictly speaking, the hardware is compatible with PS2/bidirectional, but only if the transfer software handles all of the EPP handshaking.
Also, I highly recommend getting an adapter for it instead of using batteries. Batteries usually work okay for a while and then you suddenly got odd flaky behavor as the voltage begins to drop.