Well, good news: the University of Maryland music library has a whole special collection devoted to Handel, so my quest for a public domain copy of the Messiah full score looks to be achievable.

Meanwhile, I'm nearly finished typesetting the first movement of Mozart's 25th Symphony for Mutopia, and that gives me new appreciation for Tom Lerher's old joke:

There are certain people who make you realize how little you've accomplished in life... For instance, by the time Mozart was my age, he had been dead for six years.