Why? We all know what "source available" mean and that it's not really open-source.
1. Release the source only for the purpose of studying it. Say some scientific software library's source available so you can check the details of the algorithm.
2. Release the source, and allow you to make improvements to it, but not give any further distribution rights.
3. Release the source, and allow non-commercial users to improve the source and distribute those improvements to other non-commercial users.
4. Release under some dual license.
5. Release under certified Open Source licenses.
I would say, most people would only label 1 or 2 as "source available". Over the past few years 3 and 4 are becoming more popular (for whatever reasons - good or bad). So 3 should have a name as well.
honestly, i wish the spirit behind that license were easier to formalise and publish - it roughly says "look, this is a game i made and am selling, and i don't want people taking this repo and just cloning the game for free. but we are a community of people making games, and i would love to provide the code and other assets as building blocks that will let other people make their own games more easily."