Why did it take so dang long for Indiana Jones and the Infernal Machine to be released on GOG?

My guess is that it just took that long to get it into a state where it was considered releasable- it's a notoriously difficult game to run smoothly on anything other than period-appropriate hardware.

I hid it in my dirty undies and then forgot about it. Sorry 'bout that.

It's a long story.

You see, aliens abducted the master copy and encased it in a crystal thingy (kind of a blobby shape, definitely not a skull), then sent it back in time for safekeeping, burying it in ancient northern Africa. Then Nazis unearthed it in the early '40s and sent it back to Germany, intending to use it for not-good purposes; GOG's grandparent, a Polish resistance fighter, had to fight their way into Germany to steal it back (inexplicably having to solve a couple puzzle mechanisms in the process), but died before they could personally carry it to safety -- but not before they managed to mail it to a Russian friend.
Years later, the crystal thingy fell into the hands of a sinister cabal within the Soviet Army, but GOG's parent -- having received a deathbed letter from their late parent's old friend, telling them of the mysterious, priceless relic -- tracked it down and wrested it back from them in a very action-packed manner.
After traveling the world with this mysterious crystal thingy for several years, having many more swashbuckling adventures along the way, GOG's father unfortunately became a drug addict and sold the crystal thingy for some smack. Eventually, it turned up in North Korea, where it was apparently being used as Kim Jong-Il's wig stand, when a young GOG, fresh out of school and looking for adventure, got wind of the whereabouts of this fabled artifact. Stealing a disguise in a humorous-but-still-exciting way, GOG sneaked into the country and into the very compound where the ruler lived, managing to once more recover the thingy from the forces of not-good-ness, buckling as many swashes as possible in the process.

After this exciting escapade, GOG went home and settled down, becoming a semi-successful business; the crystal thingy was put in a closet and forgotten about.
It was actually GOG's irresponsible younger sibling that fairly recently discovered the game within when they were crashing at GOG's place for a couple months: they found the crystal thingy in the closet and tried to hollow it out to use it as a bong. From there, it was a fairly simple matter to get the game working, and work out the rights with Disney.

And you know what? After removing the master copy of Indiana Jones and the Infernal Machine, the hollowed-out crystal thingy did make an excellent bong.

I'm Commander Shephard, and this is my favourite post on the Citadel.