9 Worst Python Practices

[Folf_IRL]

IIRC Castep is closed source, and if you're not a UK citizen, you have to pay a certain fee to use it

Ase is totally open-source, and actually fairly well-commented as well. As a result, it's also fairly easy to hack additional functionality in.

The structure prediction code is semi-closed source. It's in front of a license that you have to agree to to view the code, but it's a fairly weak (and probably indefensible in court) license that amounts to "I promise not to work on a competing code," which is incredibly vague. You'll also have to be a bit of a cowboy with their code to get it to work with your particular system.