We don't do planned obsolescence in the software freedom world. We keep old software and hardware usable way past its intended expiration date. If something is usable and does the job there's no reason to throw it away - and, remember, since it's free software anyone interested can fork it and bring new life to it.
Of course, with old software and hardware there are security considerations to keep in mind - I wouldn't use an abandoned web browser, for instance. But for any app that has no network access and no or very little attack surface there's no harm in using it as long as it suits your needs.
This is proprietary software even if it's been put in a git repo (presumably without the consent of the rightsholder) and run offline.
As has been pointed out in this thread, someone already got hit with a DMCA takedown for this.