V1[]
Indications are, GLINE in SmileBasic V1 is identical to that in V2.
V2[]
GLINE is a command for drawing a straight line, 1 pixel wide, on the currently selected graphics page.
If given 4 parameters, x1, y1, x2, y2, the ends of the line will be at coordinates (x1,y1) and (x2,y2).
If given 5 parameters, the first 4 will be as above, and the fifth will be the colour the line is drawn in. If the fifth parameter is omitted, the currently selected colour is used.
V3[]
No information on SmileBasic V3.