Spring RTS Engine

http://springrts.com/wiki/GamesDownloads

Zero-K does not really fit into either category.

I would call ZKL a Game Installer but disagree with the text accompanying the download. The description states that the download will contain everything required to play and also warns that the game downloads may contain old engine versions. These are not true for the ZKL download. ZKL is also not windows only.

There is another option to download ZKL in the Universal Installers section. This download claims that ZKL runs on Linux and gives some instructions for using it as a universal lobby. I think that the inclusion of this link is confusing.

Also, the Zero-K download link on the main games page should go to http://zero-k.info/Wiki/Download instead of http://zero-k.info.

Log into wiki with forum account and you can edit it.
You might have to make new "GoogleFrog" account because wiki does not like underscores _ in name.
Until recently zkl was windows-only and advertised as universal lobby, so it is just left over from there.

The warning
(!) Old engine version included. Experience of online play might be hampered.
was not meant to be for all installers..just for some and those then had the (!) next to them. But seems no such installer remains, those games updated or disappeared.

The links all go to homepage rather than download-subpage for all games.
(less dead links when sites restructure, game download via lobbies got reliable enough that link to .sdz etc is not so important anymore)