It seems like most existing open source finite element analysis software are focused on the implicit solver (code_aster, deal.ii), instead of the explicit ones.

For the explicit solvers, I found Calculix to be a good option, and also we have impact-fem. Could you please comment on what would be your opinion on this question? Ideally, the software would be:

1) In a modern open-source community that is maintained by a group of people (such as a github project; Calculix would not be in this category in this sense);

2) Actively maintained. 

Thank you!

Best,

Shawn