On GitHub’s Twitter bootstrap pages the Base CSS page’s section on icons says this:
Glyphicons Halflings are normally not available for free, but an arrangement between Bootstrap and the Glyphicons creators have made this possible at no cost to you as developers. As a thank you, we ask you to include an optional link back to Glyphicons whenever practical.
Is there a standard form this attribution should take?
To answer my own question, the solution is presumably to attribute Glyphicons in the same way that Twitter do in the footer of the bootstrap GitHub pages, namely:
This does seem to gloss over the fact that the halflings are specifically not covered by the Creative Commons licence, but I guess if it’s good enough for Twitter then it should be okay for the rest of us.