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.
With the 19.01 release of Ukuu, the application requires a personal license which costs $11, and the source code is no longer available. Tony George, the application developer, notes the reason for this being the lack of donations, with alternatives being stopping the development or requiring a paid license:
"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."