If you are searching for a "license key" simply to get the server up and running, you can stop looking. There is no trial period, and the software will not lock you out after 30 days. You do not need to crack the software or hunt for keys on obscure forums; the official download from the developer is free and unrestricted.
Depending on your needs, you can obtain a license key through several official channels: Replacing an expired time-limited license - VisualSVN
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