Instead of writing "implemented in Erlang", why not just write "slow"?
Seriously, how else could the implementation language matter? Aside from speed, either the thing is useful or it ain't. I appreciate the warning. However, reading the press release, it seems as if the event being announced is not just releasing a new version, but actually freeing up the code. People who hope to customize it probably do need to know what language they'll be coding.