WordPress.com Theme on Site Hosted Elsewhere

I found a theme that I like called “Basic Maths” on the WordPress.com site. I found out the hard way that it wasn’t available for use on a WordPress site hosted elsewhere. Is there a way to make it work or am I only able to use the theme options available on the ww.wp.xz.cn site or through private purchase? I looked through the forums already but it’s way over my head. Is there a simple answer to this?