well I have never used it. I know its $139.95 looking at there site and they claim to have a photopost plugin that works. To my knowledge what they do is lock down the directory and when a user registers in amember to gain access to the locked area there registration is also copied to photopost user table. You would need to contact them on this plugin and if it works.
I know they use to charge for plugins etc. Looks to me like they raised the price of amember and provide the plugins free now but then you need to double check with them as well.