GitLab is a free and open source project licensed under MIT. Source code for Enterprise Edition can be found here and Community Edition here.

GitLab's UI is clean and intuitive. Each view is designed to not fill the screen with useless information.

It displays the activity in a feed-type way in the most prominent part of the view. On top of that, there's a toolbar with buttons which can filter this feed by pushes, merge events or comments.

On the left, there's a menu that displays all the links that take you to the different views. For example, a file directory which displays all the files in that repo, a commit view which displays all the commits in cronological order, a network and a graph view that display important information graphically etc...

All these details make GitLab's UI extremely intuitive and easy to use, no view is overflown with information and every view displays only the most useful and crucial information needed at that time.

Has pull request (aka. merge request) support.

Gitlab is very close to Github in use and feel, written in Ruby on Rails, open source and hosted on Github as well as on GitLab.com

GitLab is being constantly worked on and has a new release every month on the 22nd. Updating is also very easy through a single apt-get command.

With the packages available here, GitLab can be installed in two minutes.

It has private/public repositories, roles for users (master, developer, reporter, guest). All of these can be set from the user interface. Same permissions set for the UI work for the SSH as well.

The Lightweight Directory Access Protocol is an application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network.

GitLab EE adds additional functionality over CE such as support for multiple LDAP servers and group sync.

A protected master branch means that no code can be merged to master without passing a code review by an authorised developer. With GitLab this comes out of the box.

Wiki and pages support out of the box.

Has issue tracking out of the box. Creating tickets, commenting on issues, closing issues etc... It's all there out of the box.

Since 7.12 you can define a minimum number of approvers for merge requests.

GitLab CI makes it easy to set up CI and deployment for projects in GitLab. It supports parallel testing, multiple platforms, Docker containers and streaming build logs.

Snippets are similar to (well-known) GitHub "gists". They are a way to share code or have conversations about anything without needing a full git repo. The implementation here reminds more of a sort of pastebin.

A single instance can handle up to 40,000 users (requires a server with 64 core CPU and 64 GB of RAM) and it can run on multiple application servers to grow beyond that.

Git Annex enables Git to manage large files (esp binaries) without checking them into Git.

The default docker.io registry is the docker hub but you can also login to other docker registries. And GitLab provides one for all Repos that make use of this feature.

Integrates out of the box with services like Bugzilla, Pushbullet, Microsoft Team Notification and many more - one can also add own webhooks to integrate with own services.

EE is the commercial Enterprise Edition, CE is the free and OpenScource Community Edition. Features such as Cycle Analytics were first a part of the EE and are now also available in CE.

Very useful project management feature that allows you to know how long it takes to go from the idea to production.