10.8 does not have Rosetta capability.
You can either buy CS6 or move to Creative Cloud.
What you could do if you have to stick with CS2 is to have a bootable hard drive that is setup to be on Snow Leopard (10.6). For the times you need to use old software such as InDesign CS2, then restart the Mac and boot from the external hard drive into 10.6 and then you're OK. I use this method for any PowerPC programs I rarely use.