Solution: IKVM. It can recompile Java apps as .NET programs, using code that was open-sourced by Sun. There may also be some native support for IPv6 (IKVM 0.46.0.0 has some IPv6 support, but doesn't seem to work well enough yet).
*. The latest usable IKVM bin: usually announced on their weblog
*. An available Java Runtime: you'll need it to unpack some of the JAR files.
*. The latest ZIP file for OpenFire.
*. IPv6 client access may need stone installed as a service; I already have a package for that (add the extra ports to the correct stone.ini).
1. Extract IKVM to something like c:\ikvm
2. Extract OpenFire to something like c:\openfire
3. Install a working JRE as able.
4. Install the stone proxy service if you need it for IPv6 clients.
5. Copy the following batch file, and edit the SET paths to where to installed/saved steps 1-3.
6. To automatically run your chat server in the background, use Task Manager to create a new task (Vista/2008 or newer) for the openfire.exe the batchfile creates.
7. You can optionally uninstall the JRE.
Batch file to compile the software...
REM Build OpenFire with IKVM
%jrebindir%\unpack200 -r commons-el.jar.pack commons-el.jar
%jrebindir%\unpack200 -r hsqldb.jar.pack hsqldb.jar
%jrebindir%\unpack200 -r jasper-compiler.jar.pack jasper-compiler.jar
%jrebindir%\unpack200 -r jasper-runtime.jar.pack jasper-runtime.jar
%jrebindir%\unpack200 -r jtds.jar.pack jtds.jar
%jrebindir%\unpack200 -r mysql.jar.pack mysql.jar
%jrebindir%\unpack200 -r openfire.jar.pack openfire.jar
%jrebindir%\unpack200 -r postgres.jar.pack postgres.jar
%jrebindir%\unpack200 -r servlet.jar.pack servlet.jar
%jrebindir%\unpack200 -r slf4j-log4j12.jar.pack slf4j-log4j12.jar
REM Compile main
%ikvmbindir%\ikvmc -lib:%openfiredir%\lib -recurse:%openfiredir%\lib -target:exe -out:openfire.exe -main:org.jivesoftware.openfire.starter.ServerStarter startup.jar
REM Move results to BIN
move *.exe ../bin
move *.dll ../bin
move *.xml ../bin
REM Copy IKVM DLLs to BIN
copy %ikvmbindir%\*.dll %openfiredir%\bin