My understanding is that Open Source means just that - The source is open for inspection. It doesn't immediately imply that the source is open for free usage by all.
I think this would likely fall foul of clause 6, in that using the software for training ML models would likely be considered a "field of endeavor". It's not the classic application of this clause (ie. "you can't use this software for military purposes", etc), but I think it'd still be covered.
Of course, IANAL, and your lawyer's opinion might differ.