From: Tom Mueller <tom.mueller_at_oracle.com>
Date: Mon, 27 Feb 2012 11:30:42 -0600

Regarding #2, the reason GlassFish requires a JDK is to compile JSPs.
The JRE doesn't contain a Java compiler.

You might want to vote for the following issue which addresses this:
http://java.net/jira/browse/GLASSFISH-5028

Tom