I have a package that is developed in SSIS 2012 using Visual Studio 2010.
Is it possible to deploy/attach this package on SQL Server 2008
Best guess would be no. The engine to run the SSIS package would have to match the release level of the code. You have not been able to run any SSIS package on any release level below the developed level of the package (i.e. 2005 server will not run a 2008 package etc.)
It is not a license issue, it is an engine issue. The SSIS engine code changes with each release and therefore the code would be running in an engine that doesn't support the features or structure of the package.