Why do i receive an error for duplicate column during installation?

When you are attempting to update the component and you are prompted with an error message like: 'Duplicate column name 'status' SQL=-- Exceptions queries in reverse versioning order 10.0 -> 1.0' the problem could be due to an installed plugin duplicating queries.

In particular if you have a System plugin named 'MightySites' that's the problem. In such case temporary unpublish that plugin and perform the JChat installation to avoid to affect it and receive any error.