It's hard cause if you like a name, you like a name, whether someone else has that name or not.
There are many names that we like and hubby wanted but i knew people that had those names, so I refuse to have them too. Same as I used to teach dancing and I refuse to have the name of any child I have ever taught (which narrows it down alot), but I just feel funny using names that I can associate with someone else. Hubby doesn't see it as a problem, but I just don't like it.
I was gonna suggest Lucas too as an option which I love. Although, if you really really like Luke, and have your heart set on it, and your friend doesn't mind, well then it won't matter. As long as you're happy with the name.