Spectral has a CCA 3.0 License meaning you have to keep the footer credit to HTML5 UP. When you join Pixelarity (the Premium Tier of HTML5 UP) you can legally remove the credit, get support and access another 96 beautiful HTML templates.
If you want the attribution-free (remove the footer credit) version of the Spectral HTML template, head over to Pixelarity for the Premium option that includes friendly support:)
It's fully responsive, built on HTML5 and CSS3, and released entirely for free under the Creative Commons license. Hope you dig it :)