Azul C4 requires a kernel module or a specialized kernel to support all the MMU tricks that it relies on to achieve maximum performance. I don't think it's really an appropriate choice for general purpose GC in a language that's designed to be easy to deploy.

Java HotSpot's collector makes the most sense IMHO: stop the world compacting in the young generation, mostly concurrent in the tenured generation. It achieves better throughput than Azul C4 too, according to the C4 paper.