Ukuu, or Ubuntu Kernel Update Utility, a fairly popular unofficial GUI tool for easily installing the latest mainline Linux kernel on Ubuntu-based distributions, has moved to a paid ($11) licensing model with its latest 19.01 release.
Ukuu displays the list of kernels available in the Ubuntu Mainline kernel website, allowing users to easily download and install the desired version. The utility can also remove installed kernels, display the changes in the selected Linux version, display notifications when new kernels are available, and so on.
The last version of this app (v18.9) had 60,000 downloads, yet only 12 users have donated over the last 2 years. It was not possible for me to continue working on this application for free, and making it paid seemed like a better alternative than discontinuing the project.
Open-sourcing an application where you are the only developer simply increases your workload (as more and more people request changes) without benefiting you in any way. FOSS projects can be fun initially if you have the time and energy, but can become a problem as the number of users increase and the requests keep piling up.
Tony George maintains multiple projects which he tries to monetize in various ways. He offers some, like Groot or TimeShift, for free (using a donation model), while others include paid additions, like Polo (a file manager) or Aptik ( a tool for migrating settings and data from one Linux installation to another). There's also Umix, a paid Linux distribution based on Ubuntu 18.04 with Unity 7 desktop.
The Ukuu 19.01 release brings a multitude of changes, including an updated user interface with kernels grouped by series, optional automatic updates, signature verification for the downloaded packages, new command line options, and more.
Older Ukuu (Ubuntu Kernel Update Utility) versions are still open source and can be freely downloaded, so the application can still be used for free, minus the new features. The project can also be forked it there's interest.
I would love to hear what's your opinion in the comments section below.