Will it be released this year? And what do you mean by 'Public'?
Private catapult is first and public second.
Will private catapult be on mijin or something else?
Catapult will be first tested and launched on permissioned chains, which is actually a good thing. They will be stressing it to the max, and any bugs will get worked out through quick development cycles that are not possible on a public chain. Also, it is easier to deploy experimental features in a permission evironment and see what sticks with businesses and what doesn't.
When Catapult launches on the NEM network, we will have a tried and tested blockchain platform, that will have gone through more testing than our competitors.
NEM will take a while to reach its full potential, but it will be worth it.