Open source is not about your ability to charge for the software. It is about the ability of the users of your software to modify it.
"Open-source software has its roots in the culture of source code sharing that dates back to the origins of computing in the 1950s. The term was formalized in 1998 with the founding of the Open Source Initiative, succeeding the free software movement initiated in the 1980s, with the intention of overcoming the ambiguity of the word "free" — meaning both freedom and gratis — to better appeal to the business world."
https://en.wikipedia.org/wiki/Open_source
You seem to be caught up in the 'free' part of 'free software'. It does not mean 'gratis software'.