This Plugin adds a G+1 like button at the start of each topics, reply or both.
Works with wordpress 3.8.1 and bbpress 2.5.3.
1. Download this plugin using the link below
2. Go to Dashboard>plugins>add new
3. Click Upload, and select the file ‘g-plus-one.zip’
4. Click install and then activate
5. Go to settings page Dashboard>settings>bbp G plus one and set whether topics, replies or both have the G+1 button.