In late 2006, I wanted to add SCP and SFTP support to curl. I investigated the library situation for SSH support and I found that there existed two similar Open Source library contenders for this purpose, confusingly similarly named too: libssh2 and libssh.
I wanted the SSH library to work with a non-blocking API to suit curl properly, so I reached out to both the SSH library projects I had found and asked them about their current support and how they viewed the future and offered to work on providing such API and functionality myself. I thought the by far most promising and friendly response came from libssh2, so I made my choice.
In November 2006 we started to add support for SCP and SFTP to curl based on libssh2, and at the same time I started contributing improvements in the libssh2 project. In particular to make sure the API could be set to and behave in a non-blocking way.
libssh2 was founded by Sara Golemon in 2004 and she was still the lead developer when I joined the project but I soon became a co-maintainer and when Sara changed jobs in 2007 she was prohibited to contribute to the libssh2 project anymore and I became almost the primary maintainer.
I remain a maintainer of the libssh2 project, but I try to keep my activities to a minimum. Others do the real work there now.
In OpenSSF's criticality score from early 2021 in which they grade how critical Open Source projects are to the world, they ranked libssh2 as #3222 out of 102,507 (in the top 3.1%).
In their November 2022 update, libssh2 ranked #3283 out of 990,000 projects (in the top 0.33%).