The YSlow plugin has been fairly popular with developers and webmasters for years now. Yahoo has continued to support and update it, but it is facing some competition these days, notably from Page Speed, a similar tool from Google.
It may be because of the competition, or because Yahoo is looking to cut costs, or because it genuinely values the input of the community, but Yahoo is making available a version of the YSlow code under an open-source BSD license.
"You are encouraged to use the source code, learn how it works, fork it to make your own projects and enhance it with new rules, features, and whatever will improve this tool we all love," Marcel Duran, YSlow's project leader, wrote.
You can get the source code for latest version of YSlow from a dedicated GitHub. Developers are encouraged to fork the code from there and work on improvements and modifications.
If the fixes or changes are deemed worthwhile, they may be merged back into YSlow and made part of the stable version.
"Issues will now be tracked with GitHub’s public issue tracking system, enabling the community to directly contribute to the project roadmap. From now on it's up to you to help define priorities, fix bugs and enhance YSlow," Duran wrote.
While Yahoo doesn't come out and say it, it does seem that it's pretty much abandoning YSlow to the community or, at the very least, is making it less of a priority, leaving the bulk of the work to contributors and then taking the best bits and merging them in the stable version, which also gets published as an add-on for Chrome, Firefox, Opera, Safari as a bookmarklet and even for nodejs.