When I try to create multiple publisher in Merge replication, I get an error, "SQL should be configured to have Per seat licence". What does this mean and what configuration is required? Will this change affect anything else?

Also recently we got an error" Merge process could not retrieve column information for table dbo.tablename". I found a solution on net. I had to replace sp_ins,sp_sel and sp_upd stored procedures from publisher to subscriber for tables giving problems and replication worked. But we dont know why we had to replace the stored procedure. Can anyone tell me what to do to avoid such error and how the stored procedures change? We don't make any changes to these procedures because they are created automatically when replication is established.