I just tried to upload the script and the required icons here: https://www.playonlinux.com/en/app-3213.html
I screwed up, though, by not understanding how to include the script in the original submission.
I can't find a way to edit the submission myself, so if anyone could update it with the notes I pasted as messages there, thank you.
If I can make a suggestion: have the web interface issue a warning if the script is empty. I thought it was going to ask me in following step.
There's a vibrant reddit community of users of this program (https://www.reddit.com/r/ynab/) and I think some of them would like to have a simple way to install it on Linux.
Thank you for your help and I hope I can get the script approved :)