The "browser edition" that I suggested would enable you to install exactly the subset of Java that your particular program required, but would be able to download all of the other functionality on demand (and thus be fully compatible with J2SE).
As a result of the blog entry Ethan ended up taking a position at Sun in order to better influence a solution to the problem. Ethan is back with a blog entry updating his progress on slimming down the install footprint of Java.
First of all the feature is a proposal for Java 7 going under the name "Java Kernel". Ethan will be on the team responsible for implementing it. He cautions however that the idea has been attempted at least twice at Sun but both times a satisfactory size reduction was not gained. This isn't stopping anyone from trying again however. Initial investigations reveal the following comparison between a full Java 6 JRE, one with simply enough classes to print "Hello World", and one with enough classes to display an empty awt frame:
| Java 6 Runtime Environment: | 15.5MB |
| "Hello World" JRE: | 2.6MB |
| java.awt.Frame JRE: | 3.5MB |
It is important to note that these numbers are not from production useful JRE's. Such findings are a step in the right direction however. A larger question still remains ... Is Java a viable competitor to Flash, Ajax, and other browser enabling technologies if download size isn't an issue?.