Hello,
We use our own format because of several reasons:
1) The zip format has limitations that we don’t have. For example, a zip file cannot be larger than 4GB or have more than 65535 files.
2) We have removed a lot of unused headers, making that way our file smaller and faster to generate or extract.
3) As you already know, many of WordPress based websites are hosted in shared hostings that have small execution time limit for PHP scripts. We have figured out a way to surpass that issue thanks to our reloading mechanism, and that could not be possible if we didn’t have our own format.
So we think these reasons are good enough to allow us create and use our own custom archive format. Also, we are also offering you an extraction software, so there is no issue for extracting your files (although we believe that manual extraction is not necessary at all).
We are not trying to control anybody in any way, but we would like to talk with you and understand your point of view, because it’s very important for us.
Thank you!
