It’s great to know we have some dedicated people in the Ubuntu community.

Quoting from the Gnome Do Core Team PPA page:

64-bit users! There is a bug in Launchpad’s ppa that causes 64-bit mono package builds to fail, but David was in the marines for 12 years and only learned one thing- Leave no man behind. We’ve got a package for you at http://launchpad.net/do/+download

Thanks Kurt for pointing that out :)