If they have a grace period for free upgrades (say, a few months before v5 was announced), then I'm good with that.
If the article isn't just talking about recent purchases of v4, then I completely agree with you. Software isn't cheap.
Bria 4, released in May 2014[1], will not. It presumably runs on Mavericks (2013), Yosemite (2014), El Capitan (2015), and Sierra (2016), and possibly older releases, but not High Sierra.
The question is whether that's reasonable or not.
I don't know. I can understand being frustrated, for sure. That's also a pretty long lifecycle, with a clear upgrade path.
If you choose to update to High Sierra, knowing it breaks v4... maybe stay with Sierra?
I don't feel strongly about it, though.
[0] http://www.counterpath.com/counterpath-announces-release-of-... [1] http://www.counterpath.com/counterpath-launches-bria-4-softp...
I would hope that, for a period after it was known that v4 would not support High Sierra, they were given either a refund or a free upgrade to v5.
It keeps customers who bought just before a new release happy, and removes anxiety about whether you should wait until next release to buy.