Ask HN: How close is too close?

About a month ago, I was toying around with redesigning my website. I really love the simplicity of HN, so in what started as an exercise in "well, how hard would it be to copy the layout, but just use my database?" turned into something that I thought looked really good (well obviously, it was very similar to the layout on HN [differnt color, more stuff {tagging}, etc.])... How close is too close? It's pretty obviously very heavily influenced by HN, but not quite an exact copy. Is this okay? Should I take it down? I guess I'm asking because I've seen HN clones being okay in the past, but just wanted to double check before I stepped on anybody's toes (I couldn't find a license for HN...is there one?)