A short summary of the info I've read on sosaw's long thread:
(Of course it is for rooted phones only, because of the changes in .so permissions)
.img name must be gmapprom.img ,gmapsupp.img doesnt work.
The package originally posted in Chinese forum and shared here:
works on Android 4.4.4
doesnt work on Android 4.1.1/4.1.2/4.2.1/4.2.2
doesnt work on Samsung Note Android 4.3.3
doesnt work on Nexus 5 (4.4.4) Qualcomm CPU (but now see post#23)
It runs on Samsung S5
It runs on HTC M7 Unicom BNM 802w, change the map path to sdcard2, installation successful.