Linux users have been asking for a while; here it is:
http://apt.ubuntu.com/p/braid
Thanks to Jonathan Beilin for doing the necessary legwork for the game to go up there (and of course to Ryan C Gordon for doing the port).
Edit by Jonathan Beilin:
Ubuntu 11.10 notes: please ensure that you are using drivers that enable 3D acceleration. This may involve using the ‘additional’ (proprietary) drivers listed in the ‘System’ pane. Set your volume before you start the game – you may not be able to use volume hotkeys on your keyboard to adjust the volume once the game is active. You may see a black window while the game is starting. The first launch is the longest.
We’ve seen some reports of problems with the audio. We’re investigating the root of the problem; in the mean time, check out these posts in the forums:
Also of note is a list of command line switches.
Plus a word from Ryan Gordon: “If you get bad sound, try export SDL_AUDIODRIVER=alsa, and that’ll probably solve 90% of the problem cases (but if it’s working now and you try this, it may stop working).”