[salesman]

I'm in no way qualified to be giving business advice, but it's a very basic business strategy to offer one thing for cheap (or free) to encourage spending on another product. At a grocery store, pasta goes on sale, so you buy more tomato sauce. When Sony released the PS3 they took a loss on every PS3 they sold, because they expected to make up for that loss when customers purchased games for their new system. If players know that their friends won't need to upgrade to help them create a playerworld, they will be more likely to invest in a server.

Free developing, or better developer packages, could act as a "foot-in-the-door" for customers, as well. Not only might more developers lead to another popular server, but I'm sure people who are actively developing will end up upgrading anyways if/when they find a server they like. Happy customers are more willing to spend their money again.