The reason LW 4.9 requires Java 1.4 or later is that starting with Java 1.4, Sun introduced a much more efficient way to handle network traffic (java.nio, which stands for New Input/Output). This allows LW to handle more connections for the same ammount of processor usage.

In my opinion, Sun should have had their "New Input/Output" package in Java from the start; it's technology that other programming languages/systems have had in their standard libraries since the 1970s.

In any case, as mentioned above, Java 1.4 is avalable for OS X 10.2.9 and later.