The james server could not been run on 64bit Windows platform running as service. It simply misses "wrapper-windows-x86-64.exe".
The "Java Service Wrapper" JSW from Tanuki does support the 64bit service, it is just not packaged.
The license does not distinquish between 32bit and 64bit.
add "<include>windows-x86-64</include>" to "<generator>jsw</generator>" in pom.xml
add "<resource name='wrapper-windows-x86-64.exe'/> to "<by-organisation id='TanukiSoftware'>" in licensing.xml
We will supply a pull request.