//Out:rr:adsretint=(0.unknown)
//    (1.program in IntelliCAD)
//    (2.AutoCAD)
//    (3.ZwCad)
(defun dfn_cadver_isicad( / rr ac lc uc)
/*c2s: ac=is_string(getvar("PROGRAM")),
       rr=0;
       if (ac)
           { lc=strcase(ac,T),
             uc=strcase(ac);
             if (wcmatch(uc,"ICAD*")) rr=1;
             if (wcmatch(lc,"acad*")) rr=2;
             if (wcmatch(lc,"*zwc*")) rr=3;
           };
*/
rr)

AutoCAD
AutoCAD LT
ArchiCAD
Alibre
AllyCAD
BaBaCad-2020=https://www.babacad.com/enterprise_ed.php
Caddie
Chief Architect
Corel Designer
CorelCAD
DataCAD
DesignCAD
DoubleCAD
DraftSight
FelixCAD
General CADD PRO
Geomagic
IntelliCAD
MegaCAD
PowerCAD
ProgeCAD
NanoCad
Revit
Revit LT
Rhino
Spirit
SolidWorks
Terramodel
TurboCAD
VectorWorks
VersaCAD
Visual CADD
ZwCad

(defun mp-get-dwg-ver ( dwg / handle stream )
    ;; SOURCE
    ;; http://www.theswamp.org/index.php?topic=56316.msg602004#msg602004
    ;;  Return the specified drawing's version as a string representing
    ;;  the AutoCAD versions that create and support the version natively,
    ;;  e.g. "2018/2019/2020/2021". Of course drawings saved by Civil3D
    ;;  enjoy a special versioning hell that doesn't precisely follow this
    ;;  schema. Thanks Autodesk.
 
    (cond
        ((null (setq handle (open dwg "r"))) nil) ;; could not open drawing, return nil
        ((progn (setq stream (substr (read-line handle) 1 6))(close handle)))
        ((eq "AC1032" stream) "2018/2019/2020/2021")
        ((eq "AC1027" stream) "2013/2014/2015/2016/2017")
        ((eq "AC1024" stream) "2010/2011/2012")
        ((eq "AC1021" stream) "2007/2008/2009")
        ((eq "AC1018" stream) "2004/2005/2006")
        ((eq "AC1015" stream) "2000/2000I/2002") ;; was 2000i, forced uppercase
        ((eq "AC1014" stream) "R14")
        ((eq "AC1012" stream) "13")
        ((eq "AC1009" stream) "11,12")
        ((eq "AC1006" stream) "10")
        ((eq "AC1004" stream) "9")
        ((eq "AC1003" stream) "2.6")
        ((eq "AC1002" stream) "2.5")
        ((eq "AC2.10" stream) "2.10")
        ((eq "AC1.50" stream) "2.0")
        ((eq "AC1.4" (setq stream (substr stream 1 5))) "1.4")
        ((eq "AC1.2" stream) "1.2")
        ((eq "MC0.0" stream) "1.1")
        ("Doesn't appear to be an AutoCAD dwg, cue sad trombone.")
    )
)
;; Usage
(mp-get-dwg-ver (strcat (getvar 'dwgprefix)(getvar 'dwgname)))