Protex is described as 'Black Duck Protex integrates with existing development tools to automatically scan, discover, and identify software origins'. There are more than 10 alternatives to Protex, not only websites but also apps for a variety of platforms, including Linux, Windows, Mac and SaaS. The best alternative is FOSSA, which is free. Other great sites and apps similar to Protex are ScanCode (Free, Open Source), Palamida Standard Edition (Paid), Licensee (Free, Open Source) and Slic (Free, Open Source).
Ninka is a lightweight license identification tool for source code. It is sentence-based, and provides a simple way to identify open source licenses in a source code file. It is capable of identifying several dozen different licenses (and their variations).
FOSSology is an open source license compliance software system and toolkit. As a toolkit you can run license, copyright and export control scans from the command line. As a system, a database and web ui are provided to give you a compliance workflow.
WhiteSource Bolt is a FREE tool that scans all of your projects to detect vulnerable open source components. It provides actionable remediation paths to enable a quick fix. Available on Github & Azure DevOps Marketplaces: bolt.whitesourcesoftware.com.