Tree requirments for Linux install into existing tree

I am in the planning stages to move my GroupWise 8 installations from Netware 6.5 to Linux.

From my understanding, I thought the tree needs to be at DS 8.8.x to install a Linux server. The question I have is my Netware 5.1 servers. I need to keep at least one of them for an old Btrieve application that does not run correctly with Btrieve on Netware 6.5.

Can I keep my Netware 5.1 server in the tree as long as it does not have a replica? Or do I need to create a separate tree just for the Netware 5.1 server.

thanks
Phil J.