You can define what your contribution is, right? You can publish any code you like under GPL, with zero further commitments as far as I'm aware. It doesn't have

You can define what your contribution is, right? You can publish any code you like under GPL, with zero further commitments as far as I'm aware. It doesn't have to be working software, it doesn't all have to be licenced the same. The copyright is still yours and you can do what you like. You can sell the software. You can enhance it and keep the enhancements proprietary and secret. You can use and sell the enhanced software without providing source code The only obligations come if a company (or individual) accepts GPL contributions from outside, because they don't own the full copyright any more and have to obide by the licence of the code they accepted from outside.