On English Wikisource, we have started marking pages needing sheet music transcription. There are currently 171 tagged.
http://en.wikisource.org/wiki/Category:Pages_containing_sheet_music
But there are thousands more that are not tagged like http://en.wikisource.org/wiki/Jana_Gana_Mana
There are at least 125 files with lilypond transcriptions on the page
http://commons.wikimedia.org/w/index.php?title=Special:WhatLinksHere/Templat... http://commons.wikimedia.org/wiki/Category:GNU_LilyPond_images
And as MZMcBride says, there are many repositories of lilypond and ABC sheet music online.
Should Wikisource hold a poll to prove we want this, and would kiss the feet of the developer who fixes the problems? :P ;-)
Does the lilypond '-safe' mode not resolve the security problems?
-- John Vandenberg