that's not what source available means to me -- it just means you can look at the source code -- what you can actually do with that code, or whether or not you need a paid license, whether you can use the code in a non-commercial case only but not commercial, all of those are nuances that would be specified in the license. There are many different options from highly restrictive to highly permissive -- the only thing they have in common is that you can see the source code.

"open source" can have restrictions too. GPL is highly restrictive because it requires any code linked with the GPL code to be GPL too.