You can download Graylog2 on the GitHub pages:
It is strongly recommended to run both the server and the web interface on a *NIX machine. Both 32 bit and 64 bit architectures are supported but keep in mind that it is strongly recommended to run MongoDB on a 64 bit system. You are for example limited to a 1GB maximum size of capped collections on 32 bit - Which is the standard collection type for Graylog2.
Find the official and user-provided installation guides in the Wikis:
There are several installation resources provided by users. These are not supported or maintained by us.
Find a Chef cookbook here. There also is a Linode Stackscript that will install a ready to use Graylog2 environment: http://www.linode.com/stackscripts/view/?StackScriptID=1970 - You can build up other auto-install solutions on top of the referenced bootstrap script.
Flavio Castelli is maintaining a
SuseGallery image that you can download as ISO or a ready to use
VirtualBox/VMWare/Xen/EC2 image.
There also is Partylog2 - A ready to install/test Graylog2 appliance available as ISO.
Bapabooie on GitHub built an Gentoo Ebuild: http://github.com/Bapabooiee/bapa_overlay/tree/master/app-admin/graylog2/