Eclipse actually requires the JDK.
I use the server VM with eclipse. Slow to start up but as I leave my machine on or hibernated for weeks running, it's nearly always in a state of optimization.
According to the Eclipse FAQ it doesn't actually need the Java SDK, just the Java JRE.http://www.eclipse.org/eclipse/faq/eclipse-faq.html#users_3
You must have a Java Runtime Environment (JRE) installed on your computer. Eclipse requires version 1.3 or 1.4 of a Java 2 Standard Edition JRE.
However, since I don't use Eclipse, this could be wrong and you could be right. ;-)
I just listed Eclipse because it looked to me as if it would just need the JRE and hence use the client JVM, like JBuilder does.
I still can't see why JBuilder (and Eclipse, in case its FAQ is right) uses the client JVM by default...