The FAQ still states you have to have Java installed to solve puzzles, although most browsers no longer support it, and the site has an alternative in HTML5.
The creator studio, on the other hand, does not seem to be available in HTML5? Is there a way I can use it anyway?
I changed my browser to Google Chrome in April and then found out that they no longer support Java. However, I can still use HTML here to play the puzzles. Also, I'm very happy with Chrome.