When you are trying to monetize your forum content, then automating the affiliate link insertion can be a good option. However there are not many companies working in this space. Most of them have specific traffic criteria and not easy to get approval for. So in case we are left with Viglink and another is skimlink. Most of the skimlinks affiliate partners are pretty strong and the revenue generation opportunity is pretty high. However they take time to go through application and manually approve each forum or blog. 

Have you tried the skimlinks on your forum?