OS X El Capitan, Apple’s next Mac operating system, has forced an indie developer to cease production of its flagship software Flavours, which allowed users to change the look and design of the operating system with "themes."

In a FAQ on the company website, Interacto, developer of Flavours, explains that with Apple’s new security policy in El Capitan, every running process is prevented from modifying system files. Flavours depended on this functionality to work.

“During all this time, we have invested lots of time, resources, love and money on Flavours development; our return was terribly poor, but at least we were paid with love and engagement from the community,” the company said in a FAQ. “Now, with OS El Capitan (10.11) announced for Fall 2015, we decided to halt all further development on Flavours.”

The restriction is known as System Integrity Protection, and Apple touted it at WWDC as solving an issue with OS X's current security. Crucial elements of the system can now only be modified by Apple Installer and Software Update.

Flavours 2, Interacto’s latest version of the software, was a redesign of the software necessitated by Apple’s interface changes in current version OS X Yosemite. Following the news, the developer has cut the price of the software by 75% to $5 and bundled in a selection of themes, describing the offering as “probably the last breath of theming on OS X.”

While iOS is known for only allowing installations from Apple’s App Store, OS X has usually avoided restricting developers on OS X. One notable exception is Gatekeeper, a feature introduced in Mountain Lion, which by default keeps programs from uncertified developers from launching. The restriction is easily lifted, however, in the Security pane in System Preferences.