Install BricsCAD and probably you'll find similarities with AutoCAD... For instance BricsCAD has appload.dfs file where are stored startup applications like *.lsp and *.des... If you put appload.dfs file in similar path where BricsCAD stores it ...\Roaming\Bricsys\... (...\Roaming\Autodesk\...) you can make AutoCAD load it's compatible files (*.lsp, *.VLX, *.fas)... - here only *.dll must be loaded through NETLOAD command and that's the same for both AutoCAD and BricsCAD...