Red Hat's OpenShift is supposed to create an uber-cloud,
allowing computing workloads to run anywhere: whether it is in corporate data centres, on any of the big public clouds or a combination thereof.
There are plenty of ways for the merger, which is the largest in IBM's history, to go wrong, however.
One question is whether the added flexibility of such mixed systems
and the promise of not getting locked into any one vendor will be enough to lure firms onto IBM's new platform.
They could shy away from the additional complexity and still prefer to put their data into one cloud.
Another is the risk of a cultural clash between IBM's still relatively strait-laced culture and Red Hat's freewheeling one.
Such concerns, in addition to the high price tag, explain why the firm's shares fell by 4% the day after the deal was announced.
And then there is the question of what the acquisition means for Watson, IBM's much-promoted AI business, which has disappointed so far.
Some have suggested that buying Red Hat could mean that IBM will turn away from Watson, instead focusing even more on cloud computing.
Yet the opposite is true: Red Hat's software containers are meant to be a vehicle to deliver AI everywhere.
The idea is that IBM's cloud failure held Watson back; now it has the chance to spread more widely.
However the merger plays out, it has already produced one big winner: opensource software,
which is developed collectively by firms that benefit from it and also by volunteer programmers.
Red Hat is the third multi-billion dollar acquisition of an open-source firm this year
after MuleSoft, bought by Salesforce for $6.5bn, and GitHub, taken over by Microsoft for $7.5bn.
Not bad for a type of code whose pioneers saw themselves as rebels fighting "evil" proprietary-software makers.
Such origins were the inspiration for Red Hat's name,
as Bob Young, the company's co-founder, once explained: 18th-century revolutionaries in America and France wore red caps during their uprisings.
Now, open-source firms look more like the establishment.