definitely if he wants her to know he's interested he should ask her himself. having her friends have her come is tantamount to "my friend over there likes you. Do you like him?" kind of stuff. k...
What could also happen is that you become really good friends and there is no pressure to make it more than a friendship, but than when one of them starts getting involved with someone else, you feel the pressure that you have to say something, because you realize you could be loosing this awesome friend... what do you do than?
give him up. Its hard (i know ive been there) but you dont want to ruin anything for them. If they are really a good friend you will want them to be happy and maybe one day you can be friends again (im still waiting for this to happen)
I don't understand-if you don't want more than friendship, why would you say anything? how would you lose them as a friend?
I agree you should not say anything, it would prevent any weirdness that could be there... By just keeping quiet, as long as the person they are with or pursuing is a good person for them and makes them happy, you will continue to have a form of the friendship you worked so hard to develop...