What is the difference between "information model" and "conceptual model"?
Conceptual Modeling, Information Modeling and Data Modeling are all terms that more or less specify the same. I do not believe there is a common consensus about these terms.

When reading the articles of the authors you refer to, I get the impression that (for these authors) Conceptual Modeling is broader than Information Modeling.

A Conceptual Model can contain actors other than only computers (e.g. humans), can contain time aspects (e.g. events, and the required reaction to these events, called Behavioral Modeling by Olivé) and can contain concepts that will not necessarily translate into a data model (“we use the name conceptual modeling for the activity that elicits and describes the general knowledge a particular information system needs to know”).

An Information Model, as used by Lee et. al., has a more narrow scope (“The initial phase for developing an information model starts with the definition of the scope of the model’s applicability. The scope specifies the domain of discourse and the processes that are to be supported by the information model. It is a bounded collection of processes, information, and constraints that satisfy some industry need”) and his modeling seems to limit itself to a subset of the conceptual model. Lee et. al. also write their article with a particular industry in mind, manufacturing, where Olivé does not limit himself to an industry.

For example, a Conceptual Model could model a company including less tangible processes such as Strategy development an Marketing, and an Information Model could model some key process of the company derived from the conceptual model, for example purchasing and logistics.

I did not read their full article. I just did a scan to find where they apparently seem to differ and, as said, there is to my knowledge no clear consensus about what each term exactly means.