SVN install instructions:
1. Go to your garrysmod folder and then enter the "gamemodes" folder.
2. Make a new folder called "gamemaster". It has to be exactly like that, no capital letters and stuff!
3. Right click and select SVN Checkout (I assume you already have Tortoise SVN installed!)
4. Paste the SVN url above into the first text field thing and hit OK.
5. Get some tea or something, it will now download all the files. Roughly 35 mb total.
6. When it's done, you have successfully installed Gamemaster!