The difference between open source and free software is mostly in the political camp the word comes from. Read the OSI definition of open source if you don't believe:

> https://opensource.org/osd-annotated

The reasons why "free software" people don't like the word "open source" are indeed political:

> https://www.gnu.org/philosophy/open-source-misses-the-point....

For software for which the source code is available, but does not give the four freedoms:

> https://www.gnu.org/philosophy/free-sw.html#content

it is common to use the word "shared source" (originally devised by Microsoft):

> https://en.wikipedia.org/wiki/Shared_source