tl;dr: Use this 1x1px PSD file to force launch Adobe Photoshop CS4.
I installed OS X 10.11 Beta, updated Java soon to realise I cannot run Photoshop CS4. I felt desperate for a while, restarted my book few times, with zero results until I suddenly opened PSD file from fellow designer.
Boom! The Photoshop was running as expected.
I asked him to create 1x1px PSD for me to test a more sherable/permanent solution. Since I’m writing this post, you know the results.
Download 1x1px Photoshop CS4 Launcher for OS X El Capitan and enjoy!