"You can't take a dying project, sprinkle it with the magic pixie dust of "open source," and have everything magically work out." -- jwz, 1999

Create that tax incentive, and 99% of publishers will slap the "open source" label on something 5 or 10 years old which is completely unmaintained, unusably buggy, and virtually unreadable. Nothing of value will be gained, and big companies will have yet another tax loophole.