If that's the goal, probably a silly way to go about it. The people who care about FOSS won't forget about their reputation, and most of the people who don't care about their reputation don't know anything about FOSS.
They probably only got clearance from their lawyers (or IBM's lawyers) just now.
A lot of proprietary software includes bits from other proprietary software that they don't have the rights to open-source. And untangling and removing those bits takes time and effort.