BEAST2 (Bayesian Evolutionary Analysis by Sampling Trees) is a Bayesian phylogenetic software package. BEAST2 focuses on modularity, which allows members of the evolutionary biology community like us to develop their own models and algorithms (see e.g. BASTA, SCOTTI, BADTRIP and POMO) within this software package.

For more details, see the paper 

https://doi.org/10.1371/journal.pcbi.1006650 

and the documentation 

https://www.beast2.org/.