The actual Open Source Definition is much like the Free Software Definition, in the letter. A source-available license wouldn't be OSI-approved, so it wouldn't

The actual Open Source Definition is much like the Free Software Definition, in the letter. A source-available license wouldn't be OSI-approved, so it wouldn't technically be open source. On the legal side, free software and open source could very well be considered sinonyms (if that makes sense). The actual difference is one of attitude and end-goals.