For development and testing purposes, I've been using an old SOWPODS dictionary file, but I don't believe it would be under license to include in an O/S project. It's also far too "lexicographically dense", including thousands of words that are hugely unlikely to ever be used in a puzzle.
If we can find or create something more suitable for use and able to be included (with attribution if necessary) the installation process would be much less difficult.