The JBoss repository has a Nexus index at http://repository.jboss.com/maven2/.index/. I think the problem is that Netbeans might not be making use of this index. I would recommend installing Nexus, adding the JBoss repo to a public group and then pointing your Netbeans instance at a local instance of Nexus.
Download Nexus from http://nexus.sonatype.org
Install it by unpacking the tar.gz or zip on your machine
Fire it up by running bin/jsw//nexus start
Go to http://localhost:8081/nexus
Log in as the default admin user: admin/admin123 is the username/password
Click on Repositories
Click the Add... button
Add a new repository for the JBoss repositorywith a remote location of: http://repository.jboss.com/maven2/
Save the new repository. (You will also want to make sure that Download remote index is selected)
Add the repository to your public group by clicking on the public group and dragging the new JBoss repository to the selected repositories.
Configure your ~/.m2/settings.xml file to have the same contents as: http://www.sonatype.com/books/nexus-book/reference/maven-sect-single-group.html
At that point, all of your repository requests are going to flow through Nexus. Nexus already ships with proxy repositories for Central. So all you did was to add in the JBoss repository and then add it to the public group. Once you do this, you'll find that your builds are going to be much, much faster.