Is it possible to claim that an API is covered by copyright, so that it can't be reverse engineered and a competing product built using a compatible API?
Likewise, can a programming language be protected by copyright, so it's not possible to make a competing compatible compiler without the permission of the author of the language?
With such knotty problems in mind, the Advocate General of European Court of Justice has just issued an opinion in the case of SAS Institute v. World Programming.
And the news is good. Unless by implementing an API the author of the competing code rips off the underlying code of the original software, then creating competing software is not an infringement of copyright. Likewise, neither is creating a functionally identical programming language.
The fundamental rule of copyright is that copyright protects the expression of ideas, not the underlying ideas themselves. APIs and programming languages are equated with ideas, and the code which implements them is equated with expression.
The opinion of the Advocate General is persuasive, but not binding on the European Court, but even so, this is certainly cause to celebrate. If the opinion is confirmed, then it's good for competition, good for startups, and good for open source and open standards.
It will be interesting to see whether the Oracle vs Google case, which considers similar issues, results in a similar conclusion.