You will likely find "cracked" versions or third-party mirrors of RSLogix 500 v8.1 on the web. Using these is highly discouraged for two reasons:
If you are migrating away from legacy AB hardware, this is a free, modern alternative, but it cannot open .RSS files. Rslogix 500 Version 8.1 Download
that prevent communication with your controller. You will likely find "cracked" versions or third-party
Once on the product page:
Avoid third-party "crack" sites or "free" download mirrors. These files often contain: that targets industrial PCs. Corrupt libraries that can crash your PLC hardware. this is a free