First of all: You don't need to download any software if you just want to make a wiki! For that, simply try the demo, or sign up for a free account.
But if you do want to run Luminotes on your own server, here is the necessary software: Luminotes server. It is licensed under the terms of the GNU GPL. To use this software, you'll need a Linux machine with Python and PostgreSQL. More details, including installation instructions, can be found within the included INSTALL file.
If you have any problems or questions, please let me know. See my contact info for details.