For better or worse, it's not that uncommon for licenses to complicate it. To take one prominent example, Microsoft Research's Z3 is completely proprietary: source-code is available but you cannot make any derivative works of it (except in-house without distribution). The famous Q array-processing language is also completely proprietary. Less restrictively, it's common for things to be released under an "academic use only" or "noncommercial use only" license.