you need to use a product called Novell Native File Access. It shipped with Netware 6 & 6.5. This "announces" the netware volumes via CIFS, NFS and AFP and then your Solaris box can mount the Netware volume. We use this feature here to run our accounting system which is Solaris based, but saved us lots of $$ by giving us a journalled file system for "free" rather than buying Veritas Foundation suite etc. It works great, just make sure you use a "soft" mount on the Solaris side. This way if you're doing maintenance on the Netware box, the Solaris box won't get hung up.
I believe you can purchase it to install on a 5.x box, although 5.1 is at end of life so I don't know if you'll be able to get support etc if you need it. If you have upgrade assurance it might be a better value to just upgrade the server & get NFA (*and new functionality like iFolder, Netstorage, Apache, mysql, ssh, etc.) for free essentially.