This is the FreedomSponsors "SponsorThis" plugin for Bugzilla.
When installed, it will add a nice, discrete "Sponsor this" link on your Bugzilla's bug pages, just below the "Importance" bit.
The link leads to a FreedomSponsors page where the user can place a bounty for that bug.
To install it, just get the latest .zip package and extract the package's contents into the "extensions" subdirectory of your Bugzilla installation, so that inside the "extensions" directory there is a new directory called freedomsponsors-bugzilla-plugin-master with some content.