That he isn't walking yet is absolutely okay.They need to be cruising by 15 months, and walking by 18 months before it is a concern. The average time to start walking is 13-15 months. You have time.
The cruising with one foot tip-toe is a bit worrisome, unless he only does that occasionally.
That could be a sign that one foot won't distend properly, or even a sign of autism (they tend to be full time or nearly full time toe walkers).
It's called toe walking. My daughter toe walked throughout her early childhood and still sometimes toe walks as a teen. It can be an indicator of many different conditions or it could just be a phase that he will outgrow.
For instance, it can be an indicator of Autism or Cerebral Palsy. My daughter has a mild form of Autism called Aspergers Syndrome.
Edit:
He may also have one leg that is longer than the other and the toe walking is done to compensate for the difference in length of the two legs.