No, it isn't a war crime to have third-party code in your repository, but I find that to upset my sense of aesthetics. Many people here seem to be of the opinion that it's good to have your whole developement team on the same version of these dependencies; I say it is a liability. You end up dependent on a specific version of that dependency, where it is a lot harder to use a different version later. I prefer a heterogenous development environment - it forces you to decouple your code from the specific versions of dependencies.
IMHO the right place to keep the dependencies is on your tape backups, and in your escrow deposit, if you have one. If your specific project requires it (and projects are not all the same in this respect), then also keep a document under your version control system that links to these specific versions.