The hickey definition is from the POV of the engineer - the creation of software with simplicity. Code that is simple, doesn't necessarily result in a piece of software that is simple for the end-user.

The tellman's version is for the end user - simplicity of use, by the user, with their existing expectation, culture and pre-knowledge. It's basically describing skeuomorphism in software (but not limited to just UI). It might be enormously complicated to create for the engineer, while it remains simple for the end-user.