There are many nodes and edges missing. It would be great if the underlying graph was on a wiki. Maybe this content could be added to Wikidata (http://www.wikidata.org/).
You may be interested in DBpedia, which gets its data from wikipedia but presents it in a structured format (for example, the page for Clojure: http://dbpedia.org/describe/?url=http://dbpedia.org/resource...), though for this case, it seems the data is already on wikipedia.
The problem with Wikipedia as the data source is that there's some goof who goes around deleting articles on programming languages which aren't prolific enough (e.g. Kernel by John Shutt). Some pages don't exist to begin with (or can't exist, because the only source of information is on the language author's own page, and doesn't meet the criteria needed to be listed).
Shame, because some of the languages not listed tend to be the most interesting ones.