Attempts to merge a 1.4 board into a fresh 1.6 beta install results in this when asked for db info:
I'm not even using SQlite
You can't run the MyBB 1.4 Merge System on top of a MyBB 1.6 forum. It won't work.
You are getting that error because SQLite 2 was depreciated in MyBB 1.6
I got similar error message with MyBB Merge System trunk version.
As he stated before you. You cannot run the 1.4 merge system with the 1.6 beta version of the board. It just will not work. This isn't a problem. When 1.6 comes out a merge system will be added. But until 1.6 is gold there will be no merge system readily available for it.