1) LibreCAD is only partially GPLv2-only, and that part is what's inherited from QCad Community Edition. It's also the part which Ribbonsoft, the original developer of QCad, refused to relicense. As far as I can tell, all new code is GPLv2+.
2) Coin3D was relicensed to GPL-compatible BSD 3-clause in December 2011.
3) OpenCASCADE was never GPLv2 and most likely never will be. It could be LGPL, but that decision was put on hold.
4) "Both LibreCAD and FreeCAD both want to use LibreDWG and have patches available for supporting the DWG file format library" — this is simply incorrect. LibreCAD team did experiment a little with LibreDWG support, but AFAIK never completed the patch. FreeCAD team never had any such patches.
5) "Again, Git master on the LibreDWG code hasn't even been touched in two years." — again, incorrect. Latest changes are from early 2012.