Thanks for reading it. That's exactly what it is meant to be. I don't feel like making every single contributor sign a CLA and manage the signed CLAs... I'd rather have that built into the licensing. And since I haven't found a license that does this, I decided to write one up. However, if such a license already exists, I'd love to see it. Would you know of any?
The article quotes this part of the Apache license, which may meet your needs: "5. Submission of Contributions. Unless You explicitly state otherwise, any Contribution intentionally submitted for inclusion in the Work by You to the Licensor shall be under the terms and conditions of this License, without any additional terms or conditions."
This is in fact exactly what I was looking for, it seems. I'm just going to remove the git repo then. As you say, if a similar license already exists, there is no need for a new one.