I'm not sure where the "plenty of implementations" that support dump but not load are to be found - to the extent that JSON is a proper subset of YAML 1.2, I guess there might be plenty of those, but that subset makes for YAML that is not particular human friendly, especially for complex data structures. Most of the links I have found are to github forks of JS-YAML that depend on node.js and/or only provide parsers.
Jeremy Faivre's yaml.js on bitbucket implements both dump and load of YAML in standalone javascript (I found it from an answer to a related stackoverflow question). It is not actively maintained, but seems to work fine for moderately complex YAML and/or javascript objects.
