This is the .NET code used by the Revit 2015-2016 family of products to support IFC, and the Revit 2012-2014 families of products to support IFC export. The open source version can override the version that comes standard with shipped Revit. Revit 2013-2016 contain both IFC export and IFC export UI overrides, which contains options not available in the regular UI, such as ifcXML and ifcZIP support. The Revit 2014-2016 versions also work for Revit LT 2014-2016, respectively.
Brilliant to get frequent updates between releases for IFC exports, and great possibility to intereact directly with the developers through the discussion forum. Still, there's a bit of a way to go before things work reliably... Also wish for a better UI to get control over what comes out.