Simple Mobile apps have been very popular among FOSS enthusiasts. I've personally been using the Gallery, Contacts and the Phone app since a few years now. It's a shame that it has come to this, will be on the lookout for their forks.
In ye old days the reigning model was a pseudo subscription where you paid for a version of a program and that's all you got, if you wanted the next version of that program you had to buy it again. This made developing updates profitable and people who didn't care to pay for the update could still use the outdated program. It wasn't perfect by any means but I feel like it was one of the better compromises compared to everything else.
Sadly with the advent of mobile apps such a model is heavily discouraged.