It is GanttProject Enterprise Edition, priced at $1000, branded with your company logo. Wait, wait, I am just kidding. We decided to miss this chance to earn lots of money and provide this feature for free in GanttProject Brno. In fact, it has always been there, but now this option is exposed in the settings dialog. Just create an image file of appropriate size (40-50 px height) and choose it in a field on Application UI option page.
Free Software Foundation is not affiliated with GanttProject and we have no information if they are using GanttProject or not. We just picked their logo for this screenshot.