I have a mysql with v5 and I want to write a stored procedure --
if I write it on a mysql 5 can I access it from any other unix server (even a server that does not have mysql 5 on it)

as long as it goes through ODBC, it is run on the server which has MySQL 5

stored procedure is stored in your database engine (read it DBMS). you access your mysql from unix,win,... and database access the procedure and run it for you.
So you could run it through any db independent mechanism such as ODBC,JDBC but not a OLEDB/ADO pair because there is no such a facility on *nix machines.
-Good luck!