The correct answer is: B. Independent of platform.
A portable program is a program that can be run on multiple platforms, such as different operating systems or different hardware architectures. This means that the program does not rely on any specific platform-specific features, and can be easily installed and run on any platform that supports the program’s programming language and runtime environment.
Option A is incorrect because a portable program is not necessarily independent from its authors. The program may still be subject to copyright and other intellectual property laws, and the authors may retain the right to control how the program is used.
Option C is incorrect because a portable program does not necessarily have wheels. A portable program is a program that can be run on multiple platforms, not a program that can be physically moved from one place to another.
Option D is the correct answer because it is the only option that is consistent with the definition of a portable program.