Software Copyright is the most common method used to protect software. A programmer automatically owns the copyright of any program they write (it does not need to be applied for) and it lasts until 70 years after the death of the author.
This article will give you a quick overview to software copyright and its basics.

What is Software Copyright?
Copyright does not protect facts, ideas, systems, or methods of operation, but instead protects the way that these things are expressed. You can outline your ideas in writing or drawings, but a copyright cannot protect the idea itself. Instead, it protects fixed, tangible mediums of expression that can be reproduced, i.e. the final written or artistic work.
Historically, computer programs were not protected by copyright because until 1974 computer programs were not viewed as fixed, tangible objects. However, in 1983 traditional copyright law was extended to include machine-readable software and the Copyright Act awarded computer programs the same copyright status as literary works. While many of the same legal principles and policies apply, there are a number of distinct issues that arise with software copyright.
How to copyright software
Software copyright is predominantly used by software developers and proprietary software owners to prevent unauthorized copying of their software. The copyright holder is typically the work’s creator, or a publisher or other business to whom copyright has been assigned. Copyright holders routinely invoke legal and technological measures to prevent and penalize copyright infringement (more commonly referred to as piracy) where works protected by copyright law are used without permission.
For works such as software and web applications, the source code is primarily where copyright exists and a copyright notice should be inserted in the headers of all source code files, help files, user manuals and/or ‘about this software’ pages, to make the assertion of copyright explicit.
Where there is no direct copying of code, line-for-line, it can be difficult to prove that copying has actually occurred. One way of trying to make copying easier to detect is to include redundant code or program components in among the real code. If an alleged copy includes the same redundant program components, even if they are not line-for-line copies, it can provide a very strong inference that copying has occurred.
Independent software vendors should be very careful about disclosing source code. If someone can independently create from scratch what you have produced, just by looking at your source code, providing that the code is substantively different then your software copyright has not been infringed. The modification of your copyrighted software for personal use may also be deemed acceptable under the caveat of ‘fair use’ and also code breaking and reverse engineering when a ‘legitimate reason’ can be provided for doing so. However, ultimately any unauthorized use of the software is deemed to be piracy or theft, in recognition of the commercial harm of infringement of copyright holders.
Software copyright can be difficult to enforce. However, using an identity-based licensing solution will ensure that you always know who your end-users are.