We have been licensing content for several years but we are always looking to find new sources of unique content. Brokers, studios, paysites all welcome.
We also have a content partner program available for content owners with paysites that would like to get joins instead of licensing their content.
More info can be found here on the CPP:
http://www.youporn.com/contentpartnerprogram/
http://www.pornhub.com/cpp