You can download Eiffel Studio and use it for free. I'm not sure what restrictions there are or capabilities that may be removed. It's included in Homebrew (mac) but it's an older version. Macports seems to have the current version available. Not sure about various Linux distros.
Here's how Eiffel Software describes the licensing for EiffelStudio:
> If you wish to earn a commercial benefit from your application and not release its source code, you must purchase the number of licenses you need for your development from Eiffel Software. After you purchase licenses, you are free to use and distribute your application the way you want (see the end user license agreement).
> If you select the Open Source license, you must release your development under an Open Source license for the benefit of the community at large.
So I'm still confused about the licensing. For the open source license, is a GPL runtime embedded in the compiled program or something?
It's not free software, because it limits the commercial use. It's more like Creative Commons Share-Alike license. I remember that back in the day, it was more restrictive. (Same applied to Plan 9, which never enjoyed the same popularity as Unix, even being technically much superior.)
Back in the day, MySQL had a license like that.
It still should be fine for free software development.
Why would the GPL get involved? Copyright is flexible because by default you don't have any rights to use someone else's creative works. They can attach whatever requirements they like to it. Here, they've said you can use it for free if you release your own software as open source. Doesn't seem like a problem.
https://dev.eiffel.com/Main_Page