he has friends in high places

There's not much I can say about this that the other ladies haven't covered yet...but here's my version anyway. Since everyone's disclosing their beliefs here, I'm going to succumb to peer pressure...I'm Christian (also of the non-freak variety, like Heather B), and I do think it's pretty impressive of him to hold fast to his beliefs, especially since he's probably all too aware of what's at stake.

Should Rubin put aside his religion for a chance to play in the NHL?
Sure, but only if he wants to. I don't really see how the two must be mutually exclusive (although admittedly, I don't have a deep understanding of Judaism). Maybe because Sundays are supposed to be our day of rest but it's not really adhered to that strictly. But anyway, if it's vital that he sits out those days, then I suppose he's going to have to make a choice. I'm suspecting though, that his religion is more important to him.

Should the league support players who follow a religion to sit out games?
No...everyone has limitations on what they can and cannot do, and it'd be impossible for the world to accommodate everyone. Ok, so it's not exactly the same, but is it discriminatory that the NHL isn't open to women (with the exception of that goalie way back...and it wasn't a real game either)? I think it's up to him to figure out how to adapt.

Should it be up to the GM, coach or player to decide if he should play?
This issue should be addressed before he's signed. There should be no forcing of any kind. I think the three should have some sort of agreement that they can all live with.

Is it discriminatory to make a player get on the ice?
If he's been signed with the full awareness that he will not be participating on certain days, then yes. The GM knew what he was taking on.

So basically, I don't think the NHL owes it to him at all to make his life easier. That being said, if he manages to make it there, he shouldn't have to abandon his religious practices either.