Not the commenter you replied to, but I noticed that it depends on Redis and Mongo, which are proprietary database products. However, there are Redis and Mongo mostly-compatible DBs that are Open Source, so you can probably swap them in (though the project may not officially support them and test with them, so you may have to be willing to contribute testing and bug fixes yourself).
As someone seeking a purely open source forms solution, what do you mean by this?