As a developer currently working on a Web app that uses a Java/Tomcat backend, the recent announcement by Apple to deprecate Java is causing me some consternation. Mainly because I'm planning on hosting this Web app on Mac OS X Server (already on 10.5, soon to be on 10.6).
From http://www.appleoutsider.com/2010/10/22/java/:
Since the Intel transition, building a server VM for Darwin is almost trivial.
Is this actually true? Is there a document somewhere that describes how to build a headless Java VM for Mac OS X Server?
Build instructions for OpenJDK on OS X Snow Leopard can be found at http://wikis.sun.com/display/OpenJDK/BSDPort. Apparently. Tomcat runs fine with OpenJDK, so you shouldn't have any real problems (even if Oracle never step up and provide an "official" JDK).
You should be able to build OpenJDK on Mac OS X without much trouble. It only has Windows and X11 frontends but since you are asking for a headless JVM, this should not be a problem for you.
Pre-built binaries of OpenJDK are also available for Mac OS X. See the SoyLatte project (a Java Research License may be required):
Note that SoyLatte has recently become part of the OpenJDK BSD-Port project: