Same here. Antlr is great, finally the wait for reintroduction of C++ support is over. Never nice to see features removed in newer releases of software you want to use.
Looks interesting! From the website, it is difficult to say how this software is different to existing solutions like for example rocketcake. I guess it is more useful for creating HTML ads?
Also, what if google decides to shut this down suddenly someday? Will it be easy to switch a project to a different software then?