If a fellow designer supplies me with a font, can I use it legitimately or pay up?

I got a lovely font from a fellow designer that I’d love to use in a design. (And I mean, lovely) I read this thread but it ended up getting little off track.

I’d like to use it as a tag line for a logo, but it’s an expensive typeface. (All the good ones are.) I own Adobe Font Folio, so it’s not like I’m a leech, but it’s just so damn nice. Please advise…