Music engraving by LilyPond 2.1x.xx—www.lilypond.org, that is automatically added to your scores.
Not only can you fully remove it, by setting the tagline variable to f (just add tagline = ##f in your header block), but you are also welcome to translate it (and the LilyPond authors invite you to do so if you want to promote this great software) or customize it the way you like it!
In this snippet, we have taken the original tagline definition in the titling-init.ly file, and therefore we can tweak it the way we want. The right version number will automatically be added.