Microsoft, EMC, and NetApp have backed Oracle in its long-running dispute with Google over Java, decrying the original verdict which suggested APIs could not be copyrighted.
The firm's are up in arms over last year's court ruling which fond that Oracle is unable to claim a copyright on parts of Java code found in the Android mobile OS.
Microsoft, EMC, and NetApp wrote in a co-sponsored legal brief that the ruling undermines current copyright law.
"The district court's holding that critical elements of the software platform at issue in this case are not copyrightable at all is the product of several significant errors of copyright law," the firms said.
The ruling would remove incentives for innovation in the software industry, they added.
"In particular, the court failed to appreciate the key distinction between the threshold question of what is copyrightable and the role of separate doctrines to determine when a valid copyright has been infringed."
Oracle had originally sued Google for copyright infringement of its Java platform two years ago. The database giant alleged that Google was illegally copying Java APIs for use in its Android OS.
Late last year, a US district shot down Oracle's case. The judge ruled that Oracle could not own the copyright on pieces of code.
He found that while Oracle could own the rights to Java, it did not have the copyright on specific lines of code in the platform.
Oracle launched an appeal against the API ruling earlier this month.