Commercial software represents the majority of software purchased from software publishers, commercial computer stores, etc. When you buy software, you are actually acquiring a license to use it, not own it. You acquire the license from the company that owns the copyright. The conditions and restrictions of the license agreement vary from program to program and should be read carefully. In general, commercial software licenses stipulate that
- the software is covered by copyright,
- although one archival copy of the software can be made, the backup copy cannot be used except when the original package fails or is destroyed,
- modifications to the software are not allowed,
- decompiling (i.e. reverse engineering) of the program code is not allowed without the permission of the copyright holder, and
- development of new works built upon the package (derivative works) is not allowed without the permission of the copyright holder.