‘techy’ fix: (requires php experience)
the bbp_has_topics() function appears to function almost exactly like the wordpress loop.
In the bbpress plugin folder /bbp-includes/bbp-topic-template.php line 68 is the bbp_has_topics function.
It takes the parameter post_parent which you can assign as the id of the forum you are trying to pull posts from. There are also a number of other parameters you can set as well.
‘non-techy’ fix: someday I am guessing there will be a widget available which will let you make the filters with a gui.
@anointed Thank you for the suggestions! I searched for the codes and it seems it’s very nicely written about almost all the functions, I just added a couple of lines in the the widget core (since I don’t know much about tweaking the codes without fixing the core..) and it works great! Thanks for making the forum plugin again. It’s really a seamless and powerful integration of forum and WP!
I’d be really careful about changing core files as you loose changes on every update. Depending upon what you did, you may be best off copying the code to your theme functions file, renaming the functions, and storing it there so you don’t loose the changes.