Create animated PNGs (APNG)
I have only used APNG Assembler for Windows. It appears that the GUI version is only for Windows, but command line versions exist for both Linux and Mac OS X. Using the CLI version (or writing a UI wrapper for it, if you have any development experience) may be a possibility. 

Alternatively, you can use an online service such as this online APNG Assembler. I cannot vouch for the effectiveness of this solution, however.