I am currently thinking about open-sourcing a project of mine and am in the process of preparing the source code and project structure to be released to the public. Now I go
I wouldn't release the key publicly. The whole point of having a signed assembly is that people can trust that you're the only one who touched the binary, and so if there is any illegitimate code added then the signing is off and people know not to trust the assembly.
Signing assemblies protects you from other people adding "bad" code to your binary and pretending it's a legitimate release.