This really seems wrong to me. It should be solved by making sure that the folder name matches the folder defined in the php.ini

Agree with Brian here, this does not look like a valid fix to me, especially as it relates to what is supposed to be a security setting.

Hello!

As wrote in \Joomla\CMS\Installer\Adapter\ModuleAdapter::loadLanguage
source path is defined via ? JPATH_ADMINISTRATOR : JPATH_SITE constants.

As wrote in defines-files both constants are defined via JPATH_BASE.

As wrote in /index.php, /administrator/index.php, etc.
constant JPATH_BASE is defined via DIR

define('JPATH_BASE', DIR);

Commiter show simple example #18523 (comment)
when external data DIR and open_basedir value contain path in different register case.
In this case real windows paths is C:/Inetpub/vhosts/q.w10-52-37-138.qa.plesk.ru\ and C:\Windows\Temp\

So, this patch nothing affect except windows paths while windows stay case insensitive.

@SniperSister the views of JSST please

1. the current patch has a rather nasty side effect: you won't be able to create folders with uppercase letters in it, when you are using the JFolder::create on Windows - that's a BC breaking change in my opinion and shouldn't be implemented like this anyway

2. I don't see a benefit in weaking the strictness of the compare only to allow people to enter a wrong (yeeeees, I know, Win is not case sensitive, but still the path is technically wrong) openbasedir setting.

Closed as stated above.

Thanks @SniperSister