"open-source company" is kind of an subjective term at this point I guess, so hard to say.
But what can be said, is that even though IBM contributes a lot to open source, not many would claim IBM is a "open-source company" I think, at least when compared to Red Hat.
Yeah, I get that distinction, and the vagueness of the phrase 'open source' doesn't help with this kind of definition.
If IBM put US$1B into 'Linux' 22 years ago - but this was a small part of their operating budget at the time - do we look at absolute or comparative value?
If IBM buys, three years ago, RedHat for US$34B, does that mean IBM is now the biggest 'open source' company? (If so, the next question is obvious.)