Post date: Feb 11, 2015 10:45:50 AM
For academic and personal use it is free! (but only for Windows platform)
Cognitum has developed what they call "Controlled English" or "Controlled Natural Language (CNL)" that they use in their editor. This is more easily understood by "mere humans"; OWL has very technical and precise language to describe ontologies that can be daunting for the beginner.
You can export from the CNL format to OWL, and for pedagogical purposes this can be an excellent path to learn the more formal language.
There is a connection with R (also free!) that is very exciting to explore (I like R!) and this also provides the means for Fluent to provide visualizations of ontologies. (courtesy: https://www.researchgate.net/post/what_is_the_best_ontology_editor_for_the_beginner )
Download-link: http://www.cognitum.eu/semantics/FluentEditor/