You can you use Mathematica for free if you have spare Raspberry Pi laying around. please check:

https://news.ycombinator.com/item?id=6775330

https://twitter.com/WolframResearch/status/10519497450302177...

https://www.theverge.com/2013/11/21/5130394/raspberry-pi-inc...

Yeah browsing around their web site and product pages I couldn't find anything. After I signed in to Wolfram Cloud for the first time, I got an email with a little bit of explanation of the Basic plan:

With this introductory Wolfram Cloud plan, you get:

* 200 MB of cloud storage

* 5,000 Cloud Credits per month

* Temporary cloud deployments, allowing you to publish Wolfram Notebooks in the cloud and deploy APIs for up to 60 days

No idea what a "cloud credit" gets me, and still have no idea what functionality is available compared to, say, a WolframeOne or Mathematica or Wolfram Notebook subscription (which if you upgrade from the basic Cloud account you need to pick one of those three upgrade paths, which then each have different tiers).