I think "liberal" should imply at least open source. After reading the license, it seems I can't incorporate part of the Shen compiler in my own project or add

I think "liberal" should imply at least open source. After reading the license, it seems I can't incorporate part of the Shen compiler in my own project or add features to it. While the author presents his reasons for these limits, and they may be reasonable, I don't think this makes the license "liberal". Or rather, it's only liberal relative to proprietary licenses; but this is like saying that Chinese government is "liberal" because it affords so many more freedoms than a complete dictatorship. As far as "sound" goes, it's hard to tell since I'm not a lawyer and I don't think it was ever tested in court. Assuming the license was written by a competent lawyer familiar with the relevant law, it is probably decently sound. If it was not written (or at least edited) by a good lawyer, it becomes somewhat suspect.