I found this page, which lists software (some GPL) used or useable from
Maple:
http://www.maplesoft.com/support/help/Maple/view.aspx?path=copyright
Someone interested in adding library facilities to Maxima might find
it valuable. Presumably this code works in enough environments to
make it possible to include in (some? all?) versions of Maple.
MPFR is in there which is why I found this page.
RJF