The posting form doesn't have support for the old home grown captcha anymore. It just has support for the discontinued version of recaptcha.
https://github.com/marlencrabapple/Glaukaba/blob/master/futaba_style.pl#L364-L394
Server-side captcha generation and checking code for the home grown captcha still exists.
https://github.com/marlencrabapple/Glaukaba/blob/master/captcha.pl
What do you want to do about this situation?
A quick hack I can do to piggyback mp4 support into webm_handler is to comment out some of the make_error calls that are trying to make sure it's a webm only. A small change to process_file in wakaba.pl to add mp4 support would be needed, too.
Do you want to try this?