We have threads on Indy 4 scribes Stuart, Darabont, Nathanson and Koepp. But Boam's attempt remains a mystery. Page 232 of the Complete Making of says,
Odd... Spielberg went from happy to "no saucers." It makes sense to imagine the nameless script is a Saucer Men rewrite. The book even says elsewhere the refrigerator scene was in the middle. But Lucas wanted that scene regardless of the MacGuffin. Thoughts?More script discussions took place in August and September 1994, and Stuart turned in a revised draft on February 20, 1995. "I just didn't feel it was going to work," Lucas says, "and I started working with Jeff Boam." Jeffrey Boam ultimately produced three drafts, the last dated December 18, 1995, which was retyped in March 1996. At the time Boam said, "George is very happy with the script and Steven is happy with it, too, but the next step is to get Harrison on board." (Boam passed away in 2000.)
Then in July 1996 another movie came along that dealt with "saucermen." "When Independence Day was released and was this huge hit, Steven said, 'That was such a success I don't think we should do another one,'" Lucas says. "We had a script that I was happy with, Indiana Jones and the Saucermen. But Steven said, 'We're not doing a flying saucer movie, and that's it.' So I said, 'Okay, fine. But we're not going to do an Indiana Jones movie without aliens in it, because there's no point.' So I gave up and started doing Star Wars again."