Novell Small Business 6.5 & Linux

Hello .. Need an expert to answer my Questions..

We have got a Small Business 6.5 Installed Server and it is
running an Old FoxPro2.a software on it.

Our clients are connecting from dos & windows machines from their ethernet
cards to our software.

We want to pass an operating system to make Cluster Architecture, also use
our programs more efficient on our servers.

Can We make it with Linux ? If We can So ;

1-Will it be compatible with dos Server and Novell ?
2-Can Our users connect with their windows and dos machines to our
servers ?
3-Can We use Our Hardware more efficient ?
4-Will there be a Cluster configuration?
5-And the most important thing is; How Much it costs to take Linux Suse
server and will there be client payments?