Octave 4.0.0 is the current stable release. The source distribution as well as a Windows binary installer are available for download.
The third release candidate for the upcoming 4.0.1 stable update release is available for download, please help us test and make the 4.0.1 release a success.
There may be an OctConf 2016, an announcement will be made when a time and place has been chosen.
For details on previous conferences, see Category:OctConf.