Open handed playing has NOTHING to do with the grip one uses.
Open handed play is a STYLE of drumming.
An "open handed grip" does NOT exist.
Open handed play basically (and very simplistically put) means that the left hand stays to the left of the right hand, so no crossing over when playing the hi-hat. The general idea is that one can freely work the kit this way.
There are a lot of drummers (right handed) that work with a remote hi-hat in front of them (still) using the right hand and in that manner have easier access to the open handed playing style. (In priciple, because during some complicated fills the styles can be mixed and cross over of hands is common)
Open handed play requires a high level of ambidexterity, the ultimate examples of drummers who play like that are Simon Phillips and Carter Beauford.
They use the matched grip.
Another open handed player of great virtue is Vinnie Colaiuta, who plays traditional grip.
I hope this will help the many "confused" guys who mix-up the actual grip with a certain style of drumming.
The open handed style of play will NEVER be the standard because for most of us it is not achievable to be great at it.
It is of course though a very good style to master when one plays a very big kit.
Cheers and Happy Drumming,