What is the plugin to use here?

saros

Which plugins use this forum?

To write the text ... which plugin?

peregrine

a proprietary version of buttonbar.
your version of buttonbar plugin may look slightly different but is the closest thing right now.

http://vanillaforums.org/discussion/19021/what-plugins-are-used-here-on-the-vanilla-forums-community

http://vanillaforums.org/discussion/comment/202489#Comment_202489

if it doesn't show up in your dashboard as an available plugin already - it is here ....
if you already have it in your dashboard, no need to download.

http://vanillaforums.org/addon/buttonbar-plugin