I'm not part of the team but a qualified guess would be the hosting and/or license fees. And in either case, moving from .NET to Java would seem more rational

I'm not part of the team but a qualified guess would be the hosting and/or license fees. And in either case, moving from .NET to Java would seem more rational than moving to a new functional language because they are so similar and wont require as much work. I wouldn't be surprised if there even are automatic converters.