You don't use open source software because it's better (it usually isn't).

You don't use open source software because it's freer (it only sometimes is).

You don't use open source software because it's got better politics (it isn't always).

You use open source software because *it is the only option*. In the long run, if it isn't open source, it doesn't exist.

image source: keithstack.com

As someone who was a true devotee of FutureWave SmartSketch (which became FutureSplash Animator, which became Macromedia Shockwave Flash, which became Adobe Flash, which became Adobe Animator) my sorrow is incalculable. Every day I long for software I had in the 90s which I can't find anything as good as today.
@mcc If you use open source software that isn't particularly popular, it might cease to exist as well. I used a "soundtracer" (a kind of synthesizer that you script in a language similar to that being used for POVray scenes) called "sapphire" over a decade ago, and then it suddenly vanished. I can't even find the source anymore, and the last time I downloaded the source a couple of years ago, I couldn't compile it because all the dependencies were outdated.
@LordCaramac @mcc Yeah, but at least then it would only take a sufficiently skilled group of people to make it work again, without _also_ needing to pay off greedy IP owners who'd rather see it rot.
@RogerBW @mcc The source might still exist somewhere.
@RogerBW @mcc Nope, all I can find are links to the original website that doesn't exist anymore. https://web.archive.org/web/20050901030734/http://www.pale.org/sapphire/
Sapphire

@LordCaramac @RogerBW @mcc The website has an (archived) link to the tarball with the source code: https://web.archive.org/web/20050901030734/http://www.pale.org/sapphire/sapphire_19.tgz (If the downloaded file ends in .txt for you as well just remove/change that extension to .tgz)
Wayback Machine

@Lenni @RogerBW @mcc Already ahead of you, looking at the content right now. I'm a horrible dilettante of a coder though, I don't think I can fix it.

@LordCaramac
You might want to look into running the software on an old linux version in a VM.

Yes an old Linux is unsupported and probably full of security holes. Don't let the vm talk to the Internet and you should be fine.

@dmaonR I would need a Linux from ~2008 for that, I think.

@LordCaramac The oldest liveCD I could find was Debian5 from 2009. there are 3 binaries in the tgz. all from 1998!. one is windows the other two are linux. I didn't try compiling. the binary src/sapphire maybe works? I don't know what I am looking at.

old debian: https://cdimage.debian.org/mirror/cdimage/archive/

@dmaonR I might try using the .exe with Wine. I sometimes use windows binaries from around the turn of the millennium with Wine.