While not open source, their Do-more and Click series PLCs ship with free, full-featured software for Windows.
Platforms like AWS IoT SiteWise, Azure Industrial IoT, and Google Cloud Manufacturing offer pay-as-you-go pricing with free tiers. You start with no upfront software licensing costs. open automation software crack
Many major automation vendors now offer free versions of their engineering software specifically to reduce the incentive for cracks: While not open source, their Do-more and Click