If you feel your company has the resources to take over maintenance of something like this, with the understanding that you will no longer be benefiting from the open source contributions from the community (as Python 3's VM has diverged quite rapidly, destroying a ton of projects like mod_python and Unladen Swallow), all I can say is: more power to you. However, continuing to build your empire on land we now all know to be quicksand, just so one day you have the fun job of maintaining the water table to keep your expensive buildings from sinking, seems like poor judgement.
In this case, you're not the only one building an empire on the quicksand (which by the way, was freely provided by voulenteers, which only make changes to the quicksand in an effort to _improve_ it).
The effort to keep the platform working to support your old castle will usually be shared with others, just like with the Debian project which keeps old software versions updated with backported security fixes for many, many years just so that you can sleep well each night.
This argument also never makes sense to me: I have never demanded that the Python developers change this mentality, I do not complain on their mailing lists, nor do I storm into their IRC servers demanding that they change either. And I certainly don't send them text messages at all times of the day, like thr users of my app do to me ;P.)
Instead, when there are discussions on business-oriented sites like Hacker News about what investing in technologies (like Google APIs, in this case), I make certain that people don't make flawed arguments about the cost tradeoffs involved in maintaining your own dependency chain, and it turns out that Python 2/3 is a great example of this (and one I didn't even bring up).
Unfortunately, bringing up personal stories of this tradeoff is going to come off as "whining", as you call it, to some people, but frankly that just comes off, to mr, as name calling. I think the Python 2/3 split is a great example of a particular area of quicksand that a smart businessman (which I apparently wasn't, I will add) will avoid, and I think that is an interesting idea to keep in mind ("what is the percentage chance that I will have to maintain this thing that is not my core business myself after a few years") whenever adopting a technology, new or old.
I understand that you don't mean to complain to open source projects, and that's good :)
It feels like whining to me mostly because these stories are often brought up, but rarely without any mention of the alternative: Without the wealth of open source software to build upon, we startups would either have to license the software/service or make it ourselves at great expense.
By saying that the "pro open source" argument makes no sense, you're implying that the risk exposure is more or less equivalent whether you depend on an open source stack or a proprietary web service. And to me, that's clearly wrong. There's a world of difference between someone killing your product at the flick of a switch and some piece of software becoming unmaintained a few years down the line.
Would you be a smarter businessman if you had chosen to build your software on a proprietary, well maintained programming language which would only run on Google App Engine or an Amazon web service? I certainly wouldn't think so. Still, a lot of people do something very similar, and they become surprised when they discover that the big companies don't run charities.
I'm guessing Digium would have liked it if the Skype protocol was open, _even_ if it was changing every 6 months), but it's not. Now they have to discontinue their Skype for Asterisk product because Skype changed their mind.
(To respond to your first comment for a second: I run open source projects that have tens of millions of users, so I know quite a bit about the feeling on the other side of that specific issue: those text messages I mentioned I get all the time are about bugs in something I distribute for free under the BSD license.)
You are now conflating "prorietary" with "charity", which is ironic at best, and seem to be disagreeing with my arhument not because you disagree with it's logic, but because you dislike some indirect ramification to a cause you believe in, which is sad. :(
Open Source is not some magic bullet that makes something fundamentally maintainable: it simply affects the cost of one option, which is accepting the lock in and operating the project yourself. 99% of the time it will be cheaper to take another alternative, like "migrate to another solution", which is certainly something you can do with a proprietary solution.
So no: I disagree with you; if you are choosing an open source project just because it is open source, you are a bad businessman. Example: if you chose mod_python for your web architecture today--a discontued (with prejudice: the sole remaining official maintainer hated it) project that I seem to be the only remaining user of and which (honestly, despite what I tell people) wasn't very good in the first place--over a proprietary alternative that actually had a working business model, like ASP.NET, solely because you could maintain the former yourself, that would /clearly/ be a very poor and highly costly decision for your company, and would easily allow a competitor to run circles around you on cost of development and maintenance. There may even be reasons why mod_python would be chosen over ASP.NET (such as a plausible, if painful, migration path to mod_wsgi combined with the now know to be incorrect preference of coding in Python ;P), but this one in specific is simply irrational.
As for Digium: an ecosystem (like Skype) is fundamentally different than a hosted API, and I'm confused as to why you feel it appropriate to compare them... I can replace Google Translate (an API I rely on and do not regret choosing), but I cannot replace Skype, even if the entire client were open source.
I think you should reread my post regarding "charities". I said that it's easy for people to mistake Google and other companies for charities because they provide so many free to use services.
I never said open source is a magic bullet for anything. My original point was simply that you cannot equate relying on a third-party API to relying on an open source project. There's a risk to both, but they're very different risks.
Even perpetually licensed proprietary software that you download and run yourself has the advantage that you yourself decide when you want to stop using it.
For instance, even if ASP.NET might be discontinued at some point as was VB6, nobody from Microsoft is going to come knocking on your door telling you that you need to shut down your webserver.
However, if you built your platform around Azure and used tons of services and libraries only available there, you'd have a huge problem the day the Microsoft decided to discontinue Azure or quadrupled the price.
Some APIs are easy to replace, and some are not. I brought up the Skype API because it's one that is not easy to replace. I agree that ecosystems are different, so maybe that was a bad comparison. A better example is relying on Google App Engine or Amazon EC2/EBS, or some other API that has no viable alternatives. More complex and differentiated APIs have higher value, but also higher risk since you can't move away from them as easily.
Plenty of companies do exactly this with Linux.