OSX Server has a price tag of $19.99. Some websites mention this is free for the Developers who joined as iOS Developer or Mac Developer.How to get the redemption code for the OSX server on Mavericks.

Here are few links

http://9to5mac.com/2013/10/24/apple-promoting-automated-continuous-integration-to-ios-developers-providing-free-os-x-server-copies/

http://arstechnica.com/apple/2013/12/a-power-users-guide-to-os-x-server-mavericks-edition/

The Server.app for OS X Mavericks has a price tag of $19.99. Some websites mention it to be free for Developers who joined as iOS Developer or Mac Developer.

How do I get the redemption code for the OS X Server.app on Mavericks?

Here are two Articles on the topic:

Apple promoting automated continuous integration to iOS developers, providing free OS X Server copies | 9to5Mac.com

A power user’s guide to OS X Server, Mavericks edition | Ars Technica