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Review of Open Arena powered by the Slant community.
Open Arena is a community powered open source reskin of Quake 3 with a variety of original maps and custom modes. If you're wanting to play Quake Live on Linux, Open Arena is a good alternative for you.
SpecsUpdate
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free and open source
Pro Cross-platform
Mac, Linux, and Win. And even Android.
Can run in webbrowser as shown on openarena.live