As a German working with charities, this petition doesn't make any sense/is not specific enough to know what they actually want. There is no such thing as getting an activity recognized as volunteering. You either volunteer for a registered charity, or you don't. Nobody cares what you do for a charity, whether you write code for it or clean the toilets doesn't matter for recognition.

The petition only makes legal sense if it were to ask to extend the set of charitable goals as specified in the Abgabenordnung, but the existing set already allows for FOSS projects as part of e.g. the "national education" category (public code is educative).

And, to be frank, I also don't get the "recognition" part. The tangible benefits of volunteering for a charity are limited; what does it even mean to get recognition for it.