My apologies. It does say that it's open source on the website, you are right. I merely looked at the GitHub repository and that says at the bottom that it's retired and old code. And i couldn't find any new code posted.

Also, AES is an open standard yes. I was however talking about the file format that it it structures its files as. That is very much non trivial since there are salts, IVs, mode of operation, the actual cipher, ...