The best open source alternative to sn0int is Nmap, which is both free and Open Source. If that doesn't suit you, our users have ranked nine alternatives to sn0int and six of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to sn0int are SpiderFoot (Free, Open Source), Sublist3r (Free, Open Source), OWASP Amass (Free, Open Source) and Datasploit (Free, Open Source).
SpiderFoot automates OSINT to find everything possible about your target. It integrates with just about every data source available and utilises a range of methods for data analysis, making that data easy to navigate.
The OWASP Amass Project has developed a tool to help information security professionals perform network mapping of attack surfaces and perform external asset discovery using open source information gathering and active reconnaissance techniques.
theHarvester is a very simple, yet effective tool designed to be used in the early stages of a penetration test. Use it for open source intelligence gathering and helping to determine a company's external threat landscape on the internet.