Additionally, they published this paper last year with an early demo of the editor linked on Youtube. I've posted it on here a few times but it hasn't had much response.
http://soft-dev.org/pubs/pdf/diekmann_tratt__parsing_compose...
http://soft-dev.org/pubs/pdf/diekmann_tratt__parsing_compose...
[1] http://ecoop14.it.uu.se/programme/ecoop_ss_tratt.pdf