Readability

[Safari](Safari used the Readability code (Apache 2 licensed). http://www.theregister.co.uk/2010/06/08/safari_reader_based_on_open_source_project/ ) and FF both use it.

Apache-2 licensed

Algorithm

This is roughly accurate as of the Arc90 Labs work. It needs to be updated to reflect the changes Mozilla has made since then.

Rip out some unlikely things by id and class, like "comment", "disqus", "menu", etc. (except if they're on the body tag).
Turn divs that don't contain any block elements into p tags.
Score using…
- Length of paragraphs
- Number of commas (?!)
Scale scores by link density.
Prepend and append sibling nodes of winner if…
- Their scores are ≥1/5 of the winner
- They're at least 80 chars long and have low link density or
- They're short but have no links and have at least one thing that looks like a sentence.

For our purposes, we would need…

Some output even if we aren't confident that it's the main content. Err on the side of too much.
No automatic traversal to additional pages of paginated content