Open Source is not the same as Free Software and does not say
much about the license other than that the source can be viewed.
At least that is my understanding.
Open source was coined by the guys at mozilla to avoid the ambiguity people are trying to create. Open source has a clear and well-defined meaning and it's not defined by whether the source is viewable.
Your understanding is correct. Open source means nothing more than you can view the source. It's just typically open source software also comes with a license that allows you to use it free, either with MIT or similar.
You are thinking of Source-Available Software[1], not Open Source. The sets of Open Source and Free Software licenses are (almost) identical. OSS == FOSS == FLOSS == FS, etc.
Your understanding is not correct. Open source does not only mean than you can view the source. If you're not familiar with the term, look it up. Don't make things up.