Depending on what you have on this second server, forums, secure content, etc. You are probably looking at a custom code job. That second server has to be setup to talk to S2member. I am doing a deal like that as well, and it works really slick but that server must be running a script waiting for authentication, checksums and input from s2member. You must consider what variables you are going to send. Then it's a matter of programming. This process can get very tricky. So it all depends on what level you want to take it to. If you stick with s2member you at least have 1/2 of the equation plus payment gateway done for the programmer. That's my 2 cents; Best of luck!