What became of Ihaka & Temple Lang's (2008) "Back to the Future"?

I’ve always found it curious that Lisp was considered modern even when it first came out. The amount of work to program in it was off the charts. BTW May 5 is the 50 year anniversary of the first release of S, the precursor to R. It’s fair to say that S/R have had a much longer shelf life than Lisp.