Pro Motion is a Pro Tool. I capitalize that because the Pro Tools can charge higher prices for a license to use their software, and nobody complains because professionals make that investment back right away.
Here are some other examples of Pro Tools: Adobe Creative Suite, Avid, Visual Studio and Xylinx ISE.
I picked the last two examples on purpose because Visual Studio and ISE are compilers. Visual Studio does a lot of languages but for simplicity let's assume it's just Visual C# and ISE does several languages but Verilog is arguably the most important.
The only way compilers can charge top dollar is by cheating: the open source compilers have demonstrated a higher quality, broader support, faster bug fixes and more features than their competition. Pro Tool Compilers can only exist on a closed system. For Visual C# it's Windows. For ISE it's the Xylinx patented chip architecture. It might seem impossible that enough professionals would be interested in an open source project that they would rather spend their time developing the tool they need rather than buying it, but that's what happened for C compilers. Even Apple releases XCode for free.
It may take years for other Pro Tools to become open source. The Gimp is not going to replace Adobe CS anytime soon. But it will happen eventually because as a professional I would rather have a tool I can customize to my needs. Adobe's move to always-online products is a huge turn-off for example.
So in the meantime there's a lot of money to be made by selling Pro Tools – but that's not where the market is going.
Selling a service may never be a money maker for Pro Tools; but professionals have to climb the learning curve anyway, even if they paid Adobe first. It might make more sense to look at how most professionals learn Adobe's products in the first place: they either pirate the software or learn it using someone else's copy (such as at school). They only really pay once they've entered the business world.
In the business world suddenly a service contract makes total sense! It might not be a service contract for the Gimp (hah! lol) but would it be nice if there was a company that offered enterprise training and support? Oh wait, Red hat, IBM, SAS, the list goes on and on.
Where open source would really make a difference is that anyone, anywhere in the world, could download the software for free (and not need to feel guilty about it). In fact, the feedback from professionals all over the world would be worth 100x what Adobe gets now from licensing fees.