Apple Developer Redeem Codes

OS X Yosemite DP7

OS X Server(2.2)

Old, may be upgradable.

Mountain Lion

Useless

Mavericks

Useless

For others:
Free OS X Yosemite(10.10) Developer Preview Redeem Code for Developers
Apple gives free OS X Server 3.0 redeem codes to developers

Apple Developer Redeem Codes by @sskaje: https://sskaje.me/2014/09/apple-developer-redeem-codes/

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