I haven't taken a look at any of this, and if you really need the GUI, this won't help...

They do seem to make an arm build of the command line version. On their download page, you'll see a link to download the CLI for general Linux architectures. Try extracting that archive somewhere, and running install-inform7.sh This will install it to the /usr/local directory (I would make sure you're root before running the script...)

Looking a bit more into it, this seems to use perl, so you'll need to install that. Even with perl, you're not guaranteed to have all the required perl modules that it needs to run. Good luck!

[edit]Could you also post the error messages you're getting?