The rumour a decade ago was that Adobe was the biggest producer of Adobe cracks. The idea was that it'd get people using it for free so it was the goto tool and then they could slam anyone using it commercially.
They can be still efective. Even a simple scheme may prevent a corporate user misusing some 30 day trial over and over and instead go through the trouble of getting proper license.
Yes, it's probably worth it to get a simple scheme for corporate users only. But Photoshop's protection isn't simple, but it is so widely cracked that in third world countries with limited internet access there are wandering sellers with DVDs of cracked Photoshop for 2-3$ (!)
I’m not finding much searching around either. I probably have an old spinning rust drive somewhere with the files still on them. This was somewhere around the CS5 or CS6 days, pre-subscription model.
From memory, in addition to sticking some pseudo-randomly named files in /System/Library, /Library, and -/Library, it would place a file in the root directory of all hfs+ volumes with xattrs set to hide and write-protect the file. Installers would then look for these files to check licensing status.
At the time, this was a fairly common trick with pro/prosumer proprietary software.
I believe on Windows the FlexNet DRM they use(d?) would overwrite Sector 32 and/or sometimes other nearby ones [0], which broke a fair few people’s GRUB2 bootloader installs as well as TrueCrypt as Flexera apparently didn’t check to see if it was in use for something else first.
