Sync MySQL 4.0 table to MySQL 5.6 server every few minutes
This looks interesting and might (just might) be a solution to your issue. It shows how a 4.1 server can simulate Stored Procedures (SPs - not available till version 5 of the MySQL server) using the Federated storage engine. Basically, it shows that a 5.x server can access data on a 4.x server and even update that data. It also shows that you can use 5.x to read the data also. This is probably a good fit for your requirements, however the federated engine does not support transactions. It's also covered here (Morgan Tocker is a MySQL community manager).