I joined at one time. Good site, but hasn't been updated in an age and the owner seems to be out of circulation. But for a one time membership it is certainly worth it.
As regards the billing, it is done in the same way ( through Ccbill, if I remember) that many other sites use. Is it safe? Well, is any internet transaction really safe? I put a ceiling on my card to limit any possible losses through hacking, and don't give any info about my bank account. I guess it is always a calculated risk.