Each developer has a "Donation Address" (a unique 34 character, alpha-numeric ID which is located near the Bitcoin image) enabling you to show your appreciation to a single developer, for a particular piece of software. You are under no obligations to make a donation, but all will be gratefully received and given directly to the developer. Please note, however, that a donation does not supersede, invalidate or in any way imply an alteration to the authors original licensing agreement. It is purely an acknowledgement of the authors hard work, an indication that the software was useful, and an incentive to continue development.