" it's we don't have the risk tolerance. If you disappear, or get purchased and stop offering your product, or decide not to fix our bugs because they're too niche to us, I don't want to be hung out to dry."

Lots of examples. Convergent's CTOS, OpenVMS temporarily, QNX's "open" source, most desktop OS's, many commercial compilers, and recently FoundationDB I had hopes for. I simply don't use something commercial unless I can export the data out of it easily to an OSS alternative that I have ready-to-go. Also need to regularly export and test that data as the closures or licensing changes sometimes happen without warning.