Snow theme is free. Download core package of Question2Answer 1.5.3 and you wil get Snow theme. AQUA theme is not free you must buy to use.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.