This is Coin-@VERSION@ by Systems in Motion. What you have downloaded
is only the framework itself, provided as a convienience for those who
do not want to use binary installers. To install, simply drag the
Inventor.framework to /Library/Frameworks. If you prefer, you can also
find a complete package including an installer and the Coin
commandline tools on our ftp server[0]. 

Note that this binary SDK has been built with gcc 4.0, meaning that 
no earlier version of gcc should be used in combination with this
framework. Due to the ABI changes in gcc 4.0, applications built 
against this framework can only be used on Mac OS 10.4 "Tiger" or 
Mac OS 10.3.9. If you need to deploy on earlier versions of Mac OS
X, use gcc 3.3 and the binary SDK of Coin built with gcc 3.3. For 
more information, please read the relevant FAQ entry at [1]. 

The Coin3D/Mac homepage[2] contains more information on how to get
started using Coin. You might also want to consider joining our 
public mailing list for discussions related to Coin3D development[3].

Enjoy!

[0] ftp://ftp.coin3d.org/pub/coin/bin/macosx/
[1] http://www.coin3d.org/mac/faq/#dist_tiger
[2] http://www.coin3d.org/mac/
[3] https://www.coin3d.org/mailman/listinfo/coin-discuss/