wordpress.com and ww.wp.xz.cn confusion

According to your other thread, you’ve already paid for the domain name. Using the name on WordPress.com will cost $12 a year. See http://en.support.wordpress.com/domain-mapping/
You can use WordPress.com with a <blogname>.wordpress.com address for free.

If you use ww.wp.xz.cn, you’ll have to pay for a host and the domain name. These are separate, but some hosts bundle them together. You can use any hosts you want that meet the requirements. The list on ww.wp.xz.cn is just a list of suggestions. See http://ww.wp.xz.cn/about/requirements/ for the exact requirements.

Like esmi has already said, the ww.wp.xz.cn site here provides the software download, which is free, and the support forums, which is staffed by unpaid volunteers.