The common view on copyright versus patenting is that copyright protects the expression of an idea, while a patent protects the idea itself. We have discussed this extensively in [4]. An intriguing case occurs when both, orthogonal, mechanisms are applicable to protect the same artefact.
A first line of defense is to use copyright to protect the owner of the expression (which is an embodiment of the invention) against IPR violations. A second line of defense is to patent specific ideas.
Since legal procedures involving patents imply significant legal risks and associated costs, it will be preferable to use - in case of a perceived violation - the first line of defense (copyright) whenever possible.
This combined usage of copyrights/patents is only relevant for a patent holder who actually exploits the inventions described in his patents. He can only do so by producing embodiments and these are in many cases susceptible to copyright violation. A patent holder who does not own embodiments of inventions described in the patents he owns cannot resort to copyright protection. This implies that in the standard case for which the patent system has been setup patents and copyright protection go hand in hand. Copyrighting is an indispensable tool because copyright violation is often easier to establish than patent infringement. However, patent protection is unavoidable in all cases where copyright protection falls short.
This standard case does not correspond with the current practice of software patenting. Only rarely, holders of software patents want to enforce a monopoly on the production and delivery of the inventions described in their patents. It is this strange situation where the practice of software patenting strongly departs from the philosophical background of the patent system that leads to the optical illusion that copyrighting suffices.
Patents are intended to create temporary monopolies, but in practice copyrights are misused to create such software monopolies. Given the long duration of copyright protection, this gives undesired and lengthy protection to pioneers in the market. The key problem is the excessive length of copyright protection in combination with the fact that copyright protection has not been designed for creating economic monopolies.