MirrorLess blog about mirrorless cameras with interchangeable lens

Orientation sensor on Panasonic cameras in the lens only?

It looks that way. On Panasonic Micro Four Thirds (and Four Thirds) cameras there is no orientation sensor - you need to attach lens with OIS (optical stabilization) to get correct orientation information in your photos.
What does it mean it practice?
With lens without stabilization, like Lumix 20mm/1.7 or Lumix 7-14mm, your photos will always be horizontal. You have to rotate on your computer every photo that you took vertically. A bit annoying probably.
Information from dpreview.com forum.