I’ve not got the source on my computer so I can’t give specific advice but if you’re wanting to change your default language can’t you substitute the AxCrypt.Content.resources.dll with your preferred language DLL? If the file names are all identical then this will be trivial.
It’s not a perfect solution because you won’t be able to change language throughout the UX but it’s easy. This all depends on how tidily the source code is written.
If you get stuck give MSBuild ILMerge a try!