If they could do it for less than $1m then I'm sure they would ...
... it'd be worth that purely for PR value, given how firmly they've pinned their business model to the Open Source mast.
But no one can blame IBM for looking at the multi-year due-diligence exercise they'd face and saying "Sorry guys, not in this lifetime!".
Given their shared parentage, there has to be swathes of code and patents shared between OS/2 and Windows.
Some of that may be owned by IBM and licensed to Microsoft (maybe exclusively). Or the other way round. Or jointly owned by the two of them.
But even if someone from IBM was to get Billy G and Steve B high as a kite one night and persuade them to sign away all possible claims over OS/2 in perpetuity - I'd bet big money that there's code in there licensed from dozens, possibly hundreds, of other third-parties as well.
Remember what Linus Torvalds has said about trying to move the Linux kernel from GPL2 to GPL3:
Regardless of his own (admittedly somewhat negative) opinion on the new license, he also really doesn't want to go through the nightmare of contacting every single person who's ever contributed code to it to get their agreement.
And that's something that's already open source!
Rather than trying to get IBM to throw the whole thing wide open, I'd say OS/2 die-hards should concentrate on a more modest goal:
Ask IBM what help they could give them in running it on more modern systems - maybe they could open up some of the hardware/driver levels of the code without too much grief.
As for the rest of it - I'm sure that the really useful stuff will make it into the open at some point or other.
Can't quite remember what bit of technology it was, something file-system related I think, but:
Some months ago IBM depth-charged yet another of SCO's wild allegations that something they'd contributed to Linux had been pinched from Unix - by pointing out that it was actually a subsystem that was developed for, and lifted from, OS/2!
So they're doing it - just a bit at a time!