In that case you can. But all your post authors will become not-registered users, but the names will be displayed in forum. To make all this working, after the moving wpforo tables you should add user nicknames to 'name' column in wp_wpforo_posts and wp_wpforo_topics tables corresponding to the Users ID in 'userid' column.

In other words all posts and topics 'name' fields should be updated by user nicknames based on the topic and posts 'userid' column. You should find some developer who can do this with custom SQL queries.

Once all is done you should update 'userid' column of both tables and set them 0 to allow wpForo track users as guests and read 'name' column instead of 'userid' column. Then go to Dashboard > Forums > Dashboard and click the to reset topics and posts data.

It depends on the wp_users and wp_usermeta tables.

If you can move these table identically to the target database then you can copy wpForo tables too. If these two tables are broken then wpForo has no chance to show topics and posts correctly because user information are lost. I'd recommend ask your hosting service for some backup/restoration.