"No matter what your motivation for building up free software, I welcome your contributions" is pretty accurate. Anyone should be free to contribute to make technical contributions to free software projects, regardless of the values they hold. Spreading free software means more than just spreading the software though. It means spreading the values so that people recognize proprietary software as something ethically wrong and rejecting it on that basis. I don't think we'll get rid of proprietary software (and do it in a permanent, lasting way) with anything less.