Do you know if it’s possible to convert your wpForo posts to bbPress? If it is, you could try converting your wpForo site to bbPress, then using the Discourse bbPress migration script to migrate the bbPress site to Discourse. Details about migrating bbPress to Discourse are here: Migrating from bbPress WordPress plugin to Discourse.
I’m sure it would also be possible to create a script to migrate wpForo directly to Discourse. It’s possible that you could find someone to do this work by creating a topic for it in the #marketplace category.