I'm unsure which email address I subscribed with, but there no longer seems a place on https://www.g-n-u.de/mailman/admin/grx to edit/update/change my subscription. The 'make -f makefile.lnx' wroked but seems I had to 'MAKEFLAGS=-j1 make makefile.x11.' Readme says try demomgrx, xdemogrx, which don't seem to exist. I installed mgrx on the system. Then (in test) I tried 'gcc demomgrx.c' which said the below.
d@1.cosmos:~/math/src/graphics/mgrx135/test$ gcc demomgrx.c /usr/bin/ld: /tmp/cczL0F2w.o: in function `drawing': demomgrx.c:(.text+0xef): undefined reference to `GrFilledBox' /usr/bin/ld: demomgrx.c:(.text+0x1e5): undefined reference to `GrLine' /usr/bin/ld: demomgrx.c:(.text+0x2db): undefined reference to `GrLine' /usr/bin/ld: demomgrx.c:(.text+0x3df): undefined reference to `GrLine' /usr/bin/ld: demomgrx.c:(.text+0x4e3): undefined reference to `GrLine' /usr/bin/ld: demomgrx.c:(.text+0x5cf): undefined reference to `GrLine' /usr/bin/ld: /tmp/cczL0F2w.o:demomgrx.c:(.text+0x6bb): more undefined references to `GrLine' follow /usr/bin/ld: /tmp/cczL0F2w.o: in function `drawing': demomgrx.c:(.text+0x7f2): undefined reference to `GrBox' /usr/bin/ld: demomgrx.c:(.text+0x8d3): undefined reference to `GrFilledBox' /usr/bin/ld: demomgrx.c:(.text+0x99c): undefined reference to `GrBox' /usr/bin/ld: demomgrx.c:(.text+0xa95): undefined reference to `GrPlot' /usr/bin/ld: /tmp/cczL0F2w.o: in function `main': demomgrx.c:(.text+0xb2a): undefined reference to `GrSetWindowTitle' /usr/bin/ld: demomgrx.c:(.text+0xb3e): undefined reference to `gfaz_setfont' /usr/bin/ld: demomgrx.c:(.text+0xb4f): undefined reference to `GrEventRead' /usr/bin/ld: demomgrx.c:(.text+0xbc7): undefined reference to `GrSaveContextToPpm' /usr/bin/ld: demomgrx.c:(.text+0xbe2): undefined reference to `pev_button_group' /usr/bin/ld: demomgrx.c:(.text+0xc91): undefined reference to `GrAllocColor' /usr/bin/ld: demomgrx.c:(.text+0xc98): undefined reference to `GrClearScreen' /usr/bin/ld: /tmp/cczL0F2w.o: in function `ini_graphics': demomgrx.c:(.text+0xd1e): undefined reference to `gfaz_ini' /usr/bin/ld: demomgrx.c:(.text+0xd25): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0xd3b): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0xd87): undefined reference to `GrAllocColor' /usr/bin/ld: demomgrx.c:(.text+0xd8e): undefined reference to `GrClearScreen' /usr/bin/ld: demomgrx.c:(.text+0xdf9): undefined reference to `GrCreateSubContext' /usr/bin/ld: demomgrx.c:(.text+0xe0f): undefined reference to `GrSetContext' /usr/bin/ld: demomgrx.c:(.text+0xe16): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0xe38): undefined reference to `GrCreateFrameContext' /usr/bin/ld: demomgrx.c:(.text+0xe49): undefined reference to `GrEventGenExpose' /usr/bin/ld: /tmp/cczL0F2w.o: in function `end_graphics': demomgrx.c:(.text+0xe6b): undefined reference to `GrDestroyContext' /usr/bin/ld: demomgrx.c:(.text+0xe86): undefined reference to `GrDestroyContext' /usr/bin/ld: demomgrx.c:(.text+0xe8b): undefined reference to `gfaz_fin' /usr/bin/ld: /tmp/cczL0F2w.o: in function `load_font': demomgrx.c:(.text+0xea6): undefined reference to `GrLoadFont' /usr/bin/ld: demomgrx.c:(.text+0xedf): undefined reference to `GrLoadFont' /usr/bin/ld: /tmp/cczL0F2w.o: in function `paint_screen': demomgrx.c:(.text+0xfe3): undefined reference to `GrSetContext' /usr/bin/ld: demomgrx.c:(.text+0xff8): undefined reference to `paint_board' /usr/bin/ld: demomgrx.c:(.text+0xfff): undefined reference to `GrColorInfo' /usr/bin/ld: demomgrx.c:(.text+0x100d): undefined reference to `GrJpegSupport' /usr/bin/ld: demomgrx.c:(.text+0x1018): undefined reference to `GrContextInfo' /usr/bin/ld: demomgrx.c:(.text+0x1025): undefined reference to `GrContextInfo' /usr/bin/ld: demomgrx.c:(.text+0x103e): undefined reference to `GrSetClipBox' /usr/bin/ld: demomgrx.c:(.text+0x1052): undefined reference to `GrLoadContextFromJpeg' /usr/bin/ld: demomgrx.c:(.text+0x1057): undefined reference to `GrResetClipBox' /usr/bin/ld: demomgrx.c:(.text+0x1066): undefined reference to `paint_button_group' /usr/bin/ld: demomgrx.c:(.text+0x1070): undefined reference to `paint_board' /usr/bin/ld: demomgrx.c:(.text+0x10b8): undefined reference to `GrCreateSubContext' /usr/bin/ld: demomgrx.c:(.text+0x10dc): undefined reference to `GrLoadContextFromPnm' /usr/bin/ld: demomgrx.c:(.text+0x10ef): undefined reference to `GrLoadContextFromPnm' /usr/bin/ld: demomgrx.c:(.text+0x10fb): undefined reference to `GrDestroyContext' /usr/bin/ld: demomgrx.c:(.text+0x1132): undefined reference to `GrSetContext' /usr/bin/ld: demomgrx.c:(.text+0x116c): undefined reference to `GrBitBlt' /usr/bin/ld: /tmp/cczL0F2w.o: in function `the_title': demomgrx.c:(.text+0x1198): undefined reference to `egacolors' /usr/bin/ld: demomgrx.c:(.text+0x11cc): undefined reference to `GrDrawString' /usr/bin/ld: demomgrx.c:(.text+0x11fa): undefined reference to `GrDrawString' /usr/bin/ld: /tmp/cczL0F2w.o: in function `the_info': demomgrx.c:(.text+0x1222): undefined reference to `egacolors' /usr/bin/ld: demomgrx.c:(.text+0x123e): undefined reference to `GrGetLibrarySystem' /usr/bin/ld: demomgrx.c:(.text+0x12bc): undefined reference to `GrGetKbSysEncoding' /usr/bin/ld: demomgrx.c:(.text+0x12c9): undefined reference to `GrStrEncoding' /usr/bin/ld: demomgrx.c:(.text+0x12d2): undefined reference to `GrGetLibraryVersion' /usr/bin/ld: demomgrx.c:(.text+0x1316): undefined reference to `GrDrawString' /usr/bin/ld: demomgrx.c:(.text+0x1356): undefined reference to `GrDrawString' /usr/bin/ld: demomgrx.c:(.text+0x135d): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0x139f): undefined reference to `GrDrawString' /usr/bin/ld: demomgrx.c:(.text+0x13a6): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0x13b3): undefined reference to `GrFrameDriverName' /usr/bin/ld: demomgrx.c:(.text+0x13f2): undefined reference to `GrDrawString' /usr/bin/ld: demomgrx.c:(.text+0x13f9): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0x1406): undefined reference to `GrFrameDriverName' /usr/bin/ld: demomgrx.c:(.text+0x1445): undefined reference to `GrDrawString' /usr/bin/ld: demomgrx.c:(.text+0x144c): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0x145e): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0x1470): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0x14ba): undefined reference to `GrDrawString' /usr/bin/ld: /tmp/cczL0F2w.o: in function `pev_command': demomgrx.c:(.text+0x1511): undefined reference to `GrEventParEnqueue' /usr/bin/ld: demomgrx.c:(.text+0x1643): undefined reference to `GrSetWindowTitle' /usr/bin/ld: demomgrx.c:(.text+0x1652): undefined reference to `gfaz_setfont' /usr/bin/ld: demomgrx.c:(.text+0x1657): undefined reference to `GrEventFlush' /usr/bin/ld: /tmp/cczL0F2w.o: in function `paint_foot': demomgrx.c:(.text+0x1711): undefined reference to `egacolors' /usr/bin/ld: demomgrx.c:(.text+0x1741): undefined reference to `GrSetClipBox' /usr/bin/ld: demomgrx.c:(.text+0x1748): undefined reference to `egacolors' /usr/bin/ld: demomgrx.c:(.text+0x1755): undefined reference to `GrClearClipBox' /usr/bin/ld: demomgrx.c:(.text+0x1776): undefined reference to `GrDrawString' /usr/bin/ld: demomgrx.c:(.text+0x177b): undefined reference to `GrResetClipBox' /usr/bin/ld: /tmp/cczL0F2w.o: in function `paint_animation': demomgrx.c:(.text+0x179b): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0x17bd): undefined reference to `GrCreateFrameContext' /usr/bin/ld: demomgrx.c:(.text+0x17db): undefined reference to `GrDriverInfo' /usr/bin/ld: demomgrx.c:(.text+0x17fd): undefined reference to `GrCreateFrameContext' /usr/bin/ld: demomgrx.c:(.text+0x181f): undefined reference to `GrDestroyContext' /usr/bin/ld: demomgrx.c:(.text+0x185b): undefined reference to `GrBitBlt' /usr/bin/ld: demomgrx.c:(.text+0x1885): undefined reference to `egacolors' /usr/bin/ld: demomgrx.c:(.text+0x18d3): undefined reference to `GrUTF8StrLen' /usr/bin/ld: demomgrx.c:(.text+0x18f8): undefined reference to `GrStringWidth' /usr/bin/ld: demomgrx.c:(.text+0x1937): undefined reference to `GrBitBlt' /usr/bin/ld: demomgrx.c:(.text+0x194a): undefined reference to `GrSetContext' /usr/bin/ld: demomgrx.c:(.text+0x1976): undefined reference to `GrDrawString' /usr/bin/ld: demomgrx.c:(.text+0x1985): undefined reference to `GrSetContext' /usr/bin/ld: demomgrx.c:(.text+0x19bc): undefined reference to `GrBitBlt' /usr/bin/ld: /tmp/cczL0F2w.o: in function `disaster': demomgrx.c:(.text+0x1a0f): undefined reference to `gfaz_fin' /usr/bin/ld: demomgrx.c:(.text+0x1a14): undefined reference to `_GrCloseVideoDriver' collect2: error: ld returned 1 exit status