I did consider read-only. Adds a lot of complication so holding on it for now. We may add it as a permission option but they would still need a license spot.
Yes. We started offering a subscription option about 7 years ago.
It works very well. It allows us to align the price with the value. There is a Pareto Principle (80/20 rule, or Power Law Distribution) at work here: 20% of our users generate 80% of the use. I.e., we have a small % of users who REALLY use the software, and use it for a long time. If we charged everyone the same then we’d be over charging some , undercharging others. The former could lose you sales, the latter leaves money on the table.