Difference between LanguageTool and LanguageToolPlus

Thank you, however it is still unclear to me.

When comparing the two for the premium package, when looking at the differences there doesn’t really seem to be a difference or it is not clearly stated what the difference is (see below). Is the personal dictionary the only difference? And what is the reason for two different websites/offerings? Are they different organizations? Do they make use of the same dictionaries/servers/backend?