And now something more difficult: A friend of mine has not used his SYD-> VIE companion ticket. If I would take a second award flight VIE->SYD->VIE could he use that companion ticket for the way back??

The SEN Line told me that his ticket is valid 365 days but if not used with an SEN they would charge me the difference of the miles to a regular award.
What I find quite strange is that in that case HE could charge MY additional miles without my knowledge which seems not quite correct from a legal viewpoint. Or will I have to change his ticket because I "bought" it.
And: where on this ticket I cann see that this is only an companion ticket?
Or is this info only included in the airlines computer?

Any thoughts?