Cal is moving its flagship scheduling software from open source to a proprietary license, arguing that AI coding tools now make it much easier for attackers to scan public codebases for vulnerabilities. "Open source security always relied on people to find and fix any problems," said Peer Richelsen, co-founder of Cal. "Now AI attackers are flaunting that transparency." CEO Bailey Pumfleet added: "Open-source code is basically like handing out the blueprint to a bank vault. And now there are 100x more hackers studying the blueprint." The company says it still supports open source and is releasing a separate Cal.diy version for hobbyists, but doesn't want to risk customer booking data in its c...