We provide Tkwant as free software under a BSD license as a service to the physics community. If you have used Tkwant for work that has lead to a scientific publication, we kindly ask you to cite the main paper that introduces Tkwant:
T. Kloss, J. Weston, B. Gaury, B. Rossignol, C. Groth and X. Waintal, Tkwant: a software package for time-dependent quantum transport, New J. Phys. 23 023025 (2021). [arXiv].