Membership is very easy and reliable. They use the very reputable subscriber services of TicketsClub * (run by Verotel *, the very well-known, reputable, worldwide online payment processor) and CCBill *. From the Bouttime Studios site's membership sign-up link, apparently TicketsClub (Verotel) does accept VISA card (so if that's a preferable credit card to use, use it with them instead of CCBill). If the site the processor serves shows it, I never heard of an online payment processor rejecting a VISA card account from anyone anywhere in the world for normal, legitimate use for its client (and sure as hell not if their client is based--which Bouttime Studios is--in the U.S.A. and U.S.A. subscribers want to join).
So if you have any more questions, you know how to shoot 'em an e-mail or send 'em a hard-copy letter.
* Anyone can scour the 'Net for online comments/experiences about various payment processors' trustworthiness and service. You'll probably always find bad cases of reviews, rip-offs, credit card abuse, unauthorized access, bullshit customer service, etc., ... etc., ... etc. I will testify that I've personally used both TicketsClub/Verotel and CCBill and have always received very high levels of reliability and service. I would recommend both of them and have not encountered any problems at all.
I will try again, but I think Virotel was blocking US-based customers. I could be wrong, but usually I have no trouble at all signing up for places.