The other big difference is DWG compatibility for interop with AutoCAD. QCAD has good DWG compat, but only in the commercial version. LibreCAD has not-great DW

The other big difference is DWG compatibility for interop with AutoCAD. QCAD has good DWG compat, but only in the commercial version. LibreCAD has not-great DWG support and is free. Last I remember reading about it, they were looking to get better DWG support via the LibreDWG library, but they needed to strip out and fully rewrite a bunch of old QCAD code to achieve that, due to licensing issues.