Not at all, you're obviously forgetting the lawsuit is from the copyleftists who want the code that someone else developed. Someone else who never gave theirs away as "free".
No, the lawsuit is from authors who don't want their work packaged and sold by someone else without compensation. You understand that by your position, i.e., that the GPL is invalid, that since Monsoon doesn't have ANY license to use or modify the code, that the authors can essentially claim every dollar of Monsoon's revenue.
Your logic would also invalidate end-user license agreements. If that happened, there's nothing stopping me from repackaging Windows and selling it as kevkromOS at 75% off Microsoft's prices.
This company doesn't have to publish its code under the GPL. However, doing so will likely be a much cheaper option than a court injunction to cease infringement that would probably kill the business.