There should be a real licence file around too. This is just the friendly reminder within the source. Could you did that out please?

Source Code License
Below is the license under which Volition released the FreeSpace 2 source code. Though technically not an open source license, the only restriction on use of the source code is that it may not be used commercially.

Note that this license applies only to the source code itself, not other game content, which is still governed by the license agreement at the top of this article.
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Copyright (C) Volition, Inc. 1999. All rights reserved.

All source code herein is the property of Volition, Inc. You may not sell
or otherwise commercially exploit the source or things you created based
on the source.