Quote from the Open Source Initiative definition of Open Source:
The license shall not restrict any party from selling or giving away the software as a component of an aggregate software distribution containing programs from several different sources. The license shall not require a royalty or other fee for such sale.
In practice, open source stands for criteria a little looser than those of free software. As far as we know, all existing released free software source code would qualify as open source. Nearly all open source software is free software, but there are exceptions.
First, some open source licenses are too restrictive, so they do not qualify as free licenses. For example, Open Watcom is nonfree because its license does not allow making a modified version and using it privately. Fortunately, few programs use such licenses.
Quote from the Open Source Initiative definition of Open Source:
Source
Not everyone agrees:
https://www.gnu.org/philosophy/open-source-misses-the-point.en.html