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

There are recent github commits within the past 2 weeks, but I don’t know of anyone in the computational or mathematical statistics community involved in it.

The stat project that gets any attention outside of R would be Stan, which is implemented in C++. A much less well-known project that takes a unique algebraic approach to modelling (including methods such as agent based models) would be the apophenia library, implemented in C.

github.com

GitHub - b-k/apophenia: A C library for statistical and scientific...

A C library for statistical and scientific computing

A hard copy book on its philosophy was published by Princeton University Press

modelingwithdata.org

Modeling with Data

Finally, a U.S. Census technical paper on an Algebra of Statistical Models

arXiv.org

A Useful Algebraic System of Statistical Models

This paper proposes a single form for statistical models that accommodates a broad range of models, from ordinary least squares to agent-based microsimulations. The definition makes it almost trivial to define morphisms to transform and combine...