These words are not synonymous with each other: “open” is not inherently free, “free” is not inherently open, and “free” is not inherently “Free”.
They each capture notions that are often orthogonal, occasionally related, and almost always generate tedious debates about freedom vs. free goods, open-ness vs. open-source, etc.
But setting all of that aside, Microsoft never claimed (until recent shifts towards embracing FOSS) to be building an open and non-profit foundation.
The criticisms of OpenAI are reasonable to an extent, not because they are not open, but because they made claims about openness that are looking less and less likely to be true over time.
Except they already drew that line long ago, when they started out open-sourcing their papers, models and code.
As soon as they took VC capital, it is hardly 'Open' is it? Especially when they are now giving excuses for closing off their research?:
From the technical paper [0]
>> Given both the competitive landscape and the safety implications of large-scale models like GPT-4, this report contains no further details about the architecture (including model size), hardware, training compute, dataset construction, training method, or similar.
Open could now mean available to use for free.