Author = Idiot or worse
APIs are interfaces to the code not the actual code. The code is the part that often requires original thinking. But there are numerous common problems that can use essentially identical logic. So code written in one language might have strong similarities to code written in another language; if not almost be identical.
The basis of FOSS is some sort of permissive copyright license that grants to anyone the right to obtain and modify the source code for any reason. The modified code can also be released by the modifier (check the license for any specific attribution/licensing requirements). Oracle v Google has little or no impact on the basic premise behind FOSS licensing; source code should be shared. The idiot did not bother to understand the basic tenet behind FOSS and the resultant licensing that grants users very broad rights to the source code by the copyright owner up front.