I think it's actually C++... The Lua glow property isn't the same than LAVA's C++-made glow, as far as I know. So you might have to recreate it with custom graphics.
LAVA uses the Fire_Add graphics function (see above comment for fire)
I think
(Source: FeynmanLogomaker's Graphics Function Helper)
//#TPT-Directive ElementHeader Element_FIRE static int graphics(GRAPHICS_FUNC_ARGS)
int Element_FIRE::graphics(GRAPHICS_FUNC_ARGS)
{
int caddress = restrict_flt(restrict_flt((float)cpart->life, 0.0f, 200.0f)*3, 0.0f, (200.0f*3)-3);
*colr = (unsigned char)ren->flm_data[caddress];
*colg = (unsigned char)ren->flm_data[caddress+1];
*colb = (unsigned char)ren->flm_data[caddress+2];
*firea = 255;
*firer = *colr;
*fireg = *colg;
*fireb = *colb;
*pixel_mode = PMODE_NONE; //Clear default, don't draw pixel
*pixel_mode |= FIRE_ADD;
//Returning 0 means dynamic, do not cache
return 0;
}