Well, because the change to the parser and the VIO layer were major, and because it wasn't merged, it drifted, and it really drifted as major releases were added. At this point, with the X protocol, and changes to triggers so that you can have more than one, and various other changes, it is very hard to merge. I gave a go at it, but I'm not familiar enough with the server to do it, so I gave up. I came up with a different way to run SQL in the server, and for plugging in other languages I just use the gearman UDF which runs them out of process safely (but they can't run SQL on the THD, if they want to use a connection they have to create a new one).