SSLeay is an open-source SSL tool for handling some types of Secure Sockets Layer (SSL) certificates for Web security. It was developed by Eric A. Young in 1995.
Techopedia explains SSLeay
SSLeay is provided under a BSD-type open source license. It supports some types of SSL certificates and certificate requests.
SSLeay shares a common type of interface with another SSL tool, OpenSSL. IT Experts consider OpenSSL as a "fork" project of SSLeay. Features of OpenSSL include cryptographic functionality and code libraries, as well as wrappers that make the libraries compatible with different types of code languages. Actual uses show that OpenSSL and SSLeay are used similarly, and sometimes interchangeably, and that users may have some issues in replacing one with the other, especially in some software environments.