Local CouchDB on Mac Opens New Browser Tab Every 5 Seconds
If you have another CouchDB running, then close it first (you might like to uninstall to stop it restarting on the next boot).  It seems like the CouchDB application fails when it can't get its expected port, but then restarts.  I uninstalled my CouchDB 1.6 (installed via homebrew) and am now able to run CouchDB 2.0 without this browser tabs problem!