Newgrounds.io is the successor to the old Newgrounds Flash API. We've completely re-built the server API to remove all dependencies on custom ActionScript classes.
Now, ANY platform should be able to use the API. The only requirements are the ability to encode and decode JSON objects, and post over HTTP.
Newgrounds.io is launching it's public beta today. We already have some libraries available for platforms that target HTML5, and complete documents on how you can build your own libraries from any other platform.
Newgrounds.io is going in to public beta today, so if you start using it, and need help or support, post in this thread and we'll get back to you as soon as we can.
If you plan on implementing Newgrounds.io into a platform we haven't covered yet, you should also check out the Newgrounds.io Developers Group. I'll be posting any major updates to the server API in there, so joining the group will keep you in the loop.
Now, before anyone DOES post for help in here, make sure you have already checked the Getting Started and Help pages on www.newgrounds.io, or the help documents for any Newgrounds.io libraries you are using. There's a lot of useful information already out there.
If you are interested in in-game ads, we will not be adding those to this API. The old Flash API often had issues with ad-blockers because they would occasionally block access to the entire API server, and we do not want a repeat of that with Newgrounds.io.
At some point, we will be looking at creating a standalone API for implementing ads in games, so keep your eyes open for that.
Also, we haven't implemented any NEW features at the time of this post, we were primarily concerned with updating the network interface and encryption options so the whole thing is a lot more platform agnostic.
The 'save data' feature is still being rebuilt (the old version was VERY Flash-oriented), and is not currently available. When it becomes available I'll post about it in here and in the developer group.
You can also follow the project on Twitter, I'll be posting news and changes there as well.