All HashiCorp have done is made their own future contributions subject to BSL, not relicensed any previous contribution, nor do they have the ability to do that without copyright assignment of each and every contribution, which they do not have (specifically I have never signed a copyright assignment, and nor has at least one other of the top ten contributors of all time).
Nothing about MPLv2 prevents inclusion in a commercial product provided the attribution and file-based copyleft provisions are followed.