Hi Chris,
upto release 7.0 orekit was only using a custom format (slightly modified from the original NOAA one) to load the coefficients.
This was done in order to support multiple different models (IGRF, WMM) and multiple epochs in one file.
Starting with the next release (you can already use the latest snapshot), orekit will also support the original format from NOAA, i.e. the original WMM2010 and WMM2015 files.
The file provided from Manfred contains exactly the same coefficients as the original files and is safe to use.