This type of intellectual property lawsuit is very common in Silicon Valley. It almost always happens that when software companies are bought, the culture deteriorates. Senior staff come into conflict with new management, leave, and start their own companies. The larger company then sues for the rote reasons IB cites in its suit. After some number of years, there's a settlement.
It seems to me the plaintiff rarely prevails if the code is entirely different. Essentially, a suit is a drawn-out punitive action to protect its brand and forestall competition. It's de rigueur for corporate legal departments, they're just doing their job. I doubt IB is at all concerned about its reputation, especially on these discussion boards.
It's just the software business.
