IANAL but I think this is just a copyright question - there are legit ways to use copyrighted works but you might be asking for trouble because they're still actively developing those games and that IP for today's platforms. It is probably not worth gambling your software on this.

http://www.copyright.gov/fls/fl102.html

In particular, the above link says:

"Section 107 [of the U.S. copyright law] contains a list of the various purposes for which the reproduction of a particular work may be considered fair, such as criticism, comment, news reporting, teaching, scholarship, and research."

It doesn't sound like the intended use in a commercial application falls under any of these protected categories.

"When it is impracticable to obtain permission, you should consider avoiding the use of copyrighted material unless you are confident that the doctrine of fair use would apply to the situation. ... If there is any doubt, it is advisable to consult an attorney."

It would be much cheaper to get competent legal advice from a lawyer now than it would be to defend yourself against an infringement lawsuit that might be brought against you by the copyright holders. And if you don't have the resources to defend yourself in court, it won't matter whether your usage of this content is "fair use" or not.

Since it is a LucasArts property, I would recommend you contact them directly for permission and any terms that they require.

Why don't you just make up your own stuff?

Because I really like monkey island's :)