I'm currently integrating open graph for my forum. I discovered that they had an article type and was wondering if it could be applied to my case. Only reason I ask because this sort of categorization is recommended when writing schema markup.
These are two different things. Open graph is for constructing a tile to show instead of a plain URL when sharing it over social media and chatting apps.
The schema you provided is for structuring your data and enabling special search features for your pages on Google search.
To answer your question, yes, you can use the article open graph tag for forum posts.