Microsoft, EMC and NetApp have joined an appeal by Oracle against an earlier decision in a copyright and patent infringement lawsuit against Google over Android.

The three companies filed an amici curiae brief in support of appellant yesterday, according to court records.

Amici curiae - which means "friends of the court" - are parties that are not directly involved in a litigation, but believe they may be impacted or have views on the matter before by the court.

In a filing earlier this month to the US Court of Appeals for the Federal Circuit, Oracle said that the appeals court should rule, as a matter of law, that Google's commercial use of Java in a market where Oracle already competed was not fair use.

Google was cleared last May of most of the infringement claims in Oracle's lawsuit, although it was found to have copied a few small portions of Oracle's Java code.

The main issue at trial was whether Google had copied in its Android operating system 37 of Oracle's Java APIs (application programming interfaces), which Oracle calls "packages" of source code. But the judge ruled in May that the APIs were not eligible for copyright protection under US law. Earlier, the jury found Google infringed Oracle's copyright in the packages and a computer routine called rangeCheck, but did not come to a decision on whether it could be construed as fair use, Oracle said in its filing.

The US District Court for the Northern District of California made a legal error in ruling that the infringed code and organisation of the 37 packages were devoid of copyright protection, Oracle said.

Besides Microsoft, EMC, and NetApp, software trade group BSA, Picture Archive Council of America and Graphic Artists Guild have also filed amicus curiae briefs in support of Oracle.

Microsoft and Google have recently clashed on a number of issues. The company was critical of a settlement in January between the US Federal Trade Commission and Google over the search giant's business practices and access to its standards-essential patents, calling it a "missed opportunity." The two companies compete in a number of areas include mobile operating systems, search, and services such as email.