There is some amount of cross-pollination. Mono has been using library code that Microsoft has been open-sourcing, for a while now. However, the core VMs are an

There is some amount of cross-pollination. Mono has been using library code that Microsoft has been open-sourcing, for a while now. However, the core VMs are and will remain separate, so they are very much different projects and will remain so. The bottom line is that people will have a choice of two different .NET VMs on non-Windows OSes now.