+You must first install **XCode** which comes on your installation DVD or can be downloaded from the Apple website. This package provides tools like **Git and GCC**, which are needed for successful checkout and compilation of Xonotic. Some versions of XCode come with Git and others don’t - if you don’t have Git after installing XCode get it here: [XCode installer](http://sourceforge.net/projects/git-osx-installer/files/)
+
+Cloning the Repository and Compiling
+------------------------------------
+
+To begin downloading:
+
+ git clone https://gitlab.com/xonotic/xonotic.git # download main repo
+ cd xonotic
+ ./all update -l best # download all other repos (data + game logic, maps, etc.)
+
+Now the game can be compiled and run with the following commands:
+
+ ./all compile -r
+ ./all run
+
+**Note:** if you encounter en error similar to darkplaces#111, try `./all clean && ./all compile -r -0`.
+
+You can use `./all compile -d` to create a slower unoptimized build with debug symbols but usually you want `-r` (which is also the new default).
+
+The `./all run` or `./all compile` line can be followed by `dedicated` to build or run the executable for server hosting. E.g. `./all compile -r dedicated`.
+
+The `run` command can also be followed by standard DarkPlaces commandline arguments:
+
+ ./all run +vid_fullscreen 0
+
+To update your Git clone:
+
+ cd xonotic
+ ./all checkout # switch to main branch on all repos (usually master)
+ ./all update # pull and prune
+ ./all compile -r # recompile what changed
+
+**Note:** If you intend to play on public servers, you should probably also enable the nexcompat repo to download additional textures that are used on some older unofficial maps. Use `touch data/xonotic-nexcompat.pk3dir.yes` and `./all update`. For mappers: these textures should NOT be used on new maps.
+
+***
+
+If you run into issues with the latest version you can easily revert to an older one. Since most bugs are caused by the game code rather that the engine, you just need to downgrade that repository. Inside the main xonotic repository, use `cd data/xonotic-data.pk3dir` and then `git checkout <some older commit>`. After that go back `cd -` and `./all compile` (with the optional `-r` flag).
+
+Contributing and Getting Write Access
+-------------------------------------
+
+Cloning (one of) our repos and submitting MRs from there (as in any other project) works but you won't be able to use our CI setup for the data repo (which seems to need a custom runner). It's therefore a good idea to join the Xonotic group and get push access - then you can create branches in our repos and use our CI.
+
+A condition for write (push) access is that you agree that any code or data you push will be licensed under the General Public License, version 2, with or without the “or any later version” clause. In case the directory the changes apply to contains a LICENSE or COPYING file indicating another license, then your pushed code has to be dual licensed appropriately. Subdirectories currently having a dual license:
+
+* `data/xonotic-data.pk3dir/qcsrc/lib/warpzone` - dual licensed as “GPLv2 or later” or MIT license.