This is the Arma Toolbox for Blender, a collection of python scripts that allow you to import and export P3D modles in MLOD format from/to Blender, with some extra support for things like Proxies, LOD's and other Arma-Specific things.   The Toolbox is open source and under GPL-3.0. It's hosted on GitHub.   Latest versions:
2.80: Alpha 3.0.4 for Blender 2.8x   New in this version: Significant speed-up for import and export operations   A legacy version for 2.79 is available here. 
2.79: 2.7.0 Bugfix #1 for Blender 2.XX (with XX <= 79)

Note that the 2.79 branch is only seeing bugfixes now, other than that it is at the end of its lifecycle. Future development will be done solely on the 2.80 branch.