I've bought both Acorn and Affinity over the years. W/ Affinity they're license is only good for the platform you purchased it on e.g. you can't use a windows license on your mac - you'd need to purchase 2 separate license. Considering I have a work mac and a work windows this was kind of annoying but whatever.
The thing that I encountered w/ Acorn was their license was tied to a particular version. For example a new Mac OS version came out, the version of Acorn I purchased wouldn't work w/ whatever version that was so continue using Acorn I need to purchase a new version. The part that irked me here was I only got like 1 years use out of the software. Feel like they should support n-2 or something to that effect. Not sure if things have changed.