In particular, I find the approach of using differential dose-volume histograms in the objective function interesting. I am not convinced that this approach is easily extended to pure dose-volume objectives (e.g. maximum 30% of the volume should receive 40 Gy or more). Nonetheless, I think it is worth to explore this approach further to see if it can lead to smoother objective function formulations.
The optimization method is patented. How well does this rhyme with providing the code as open source?