That seems a bit far fetched -- the GPL covers the code, not the API.
That's why I initially dismissed it as fearmongering. However, the precedent set is that Google's use of Oracle's API is 'fair use' (which happens to be over >10,000 lines of code, used in software contained in billions of 'instances' of products). Google argued that because of the fair use, any licensing restrictions should be disregarded. And they won. There's still a chance this could be appealed, however it sets a dangerous precedent. Anyone who has an API that is freely usable can have it integrated by a larger company (which could tax a smaller company's systems) with impunity towards the API's/creator's license. This also invites further speculation regarding copyright law because not even copyright experts/scholars/academics could see this ruling coming.
From the second paragraph in the first article I linked:The Oracle v. Google trial concluded yesterday when a jury returned a verdict in Google's favor. The litigation began in 2010, when Oracle sued Google, saying that the use of Java APIs in Android violated copyright law. After a 2012 trial, a judge held that APIs can't be copyrighted at all, but that ruling was overturned on appeal. In the trial this month, Google successfully argued that its use of Java APIs, about 11,500 lines of code in all, was protected by "fair use."
Richard Stallman can agree/disagree all he wants - he's simply the creator of GPL, he has no sway over it's legal interpretation beyond what has already been committed to the GPL.