That's correct.

Although, the plan I purchased "forever" for $1.99/month was then called "Pro" and included unlimited applets. They've now changed the plans and Pro now has limits while Pro+ is the unlimited plan. So, I'm getting the $14.99/month plan for $1.99. And frankly, it's far more than I need but that's besides the point; they promised us something "forever" and that was the only reason I subscribed.

I could be wrong, but I believe the term comes from inheriting property due to family lineage. Because your grandfather owned something, it's rightfully yours (for better or worse).