You might want to play around with Darktable (http://www.darktable.org). I have no affiliation other than using it a bit. I use an Olympus EM-5 and it handles the raw files just fine.
I have an E-M5 too (great camera!), but it has been out quite a while which helps out. It's still not perfect though, the color is off a bit for the E-M5's RAW images (.ORF). The GH4 images are unusable in Darktable, they look they have been through an Instagram filter. This is straight off the camera in both Darktable and Lightroom:
http://i.imgur.com/6v0mbUb.jpg