Gifcurry is an open-source, video-to-GIF maker. It's built with Haskell and works on Linux, Mac, and most likely Windows. There is both a graphical and command line interface.
Gifcurry takes your videos and makes them into GIFs. You can crop, trim, seek, add text, pick a font, alter the duration, change the size, set the quality, and save your creation as a GIF or a video.
For Mac users, head over to the read me page and follow the instructions. Eventually those instructions will become a Homebrew formula so installing Gifcurry on the Mac will be super easy.
Gifcurry hasn't been tested on Windows yet but there's no reason it shouldn't work. If you know how to build Haskell programs, go to the read me page and follow the instructions.
Found a bug? Need a feature? Can't install it? No worries. Point your browser to the issues page.