Can't open steam on Mac OS X 10.6.8

[76561198114316288]

I tried to install Steam; I click on 'install Steam', I simply drag it to my applications, then I open it and it starts downloading and when everything is downloaded, it says that Steam cannot be opened because of an error. Does anybody know how to solve this problem?

[MuskratFarms]

Steam no longer supports Mac OS X 10.6.8. You'll need to upgrade to 10.7 or later.

[thegeonosianwarrior]

Actually I just had the same error, but I opened it recently this very same day and it still worked just fine. Is it because I just updated it?

[76561198114316288]

Normally I should be able to upgrade my Mac to El Capitan. When I try, however, it says this can't be installed on my version of Mac, but on Apple's website the requirements are 10.6.8 or newer, which I have.

[Dillinger6394]

Download v10.7.5(Lion) and Steam will run https://support.apple.com/kb/DL1583?viewlocale=en_US&locale=en_US
or here http://getintopc.com/softwares/operating-systems/mac-osx-lion-10-7-2-dmg-free-download/

[IDAndreasID]

引用自 Dillinger：

Download v10.7.5(Lion) and Steam will run
or here

Please don't post illegal download links. AFAIK Lion can still be bought from Apple in the Mac App Store[www.apple.com], so an upgrade from Snow Leopard to Lion should still work using the Mac App Store installation method from inside a running Snow Leopard.

Also, there are two possible ways to get around this on Snow Leopard:

1. use a backed up copy of a previous release of the Steam client
   
2. install a newer libc++ on Snow Leopard

Both approaches to "fix" this (more correct: work around the issue) are described here in the Steam Mac forum in specific posts. (I found them because I have the same problem.)

So, if you have a backup of a previous working version of Steam, use this one. To prevent it from updating to the newest client (which obviously won't work anymore on Snow Leopard) you have to add a configuration file (link to original discussion):

引用自 jerry.barrington：

Use a text editor, and make a file with one line:
BootStrapperInhibitAll=Enable
Save it as "Steam.cfg". At 1st, I put it in ~/Library/Application Support/Steam/SteamApps/ but that didn't work. So I copied it into the Steam Application by right-click Steam -> Show Package Contents -> open Contents -> open MacOS -> put the file in there. I have the file in both places now, but I'm pretty sure it only needs to be in that last one. Now it doesn't update the Steam app, but games still update.

If you don't have a backup or want to have the newest client anyhow, you need to compile the missing newer version of libc++. This is a bit of work and you need to get some developer tools first: Xcode and MacPorts.
See the original thread for details on how to accomplish this should you be interested in this solution. I would, however, make regular backups as the Steam client remains officially incompatible with Snow Leopard, so it may stop working again with a newer version of the client... in which case you will be happy to have saved that last working backup...