Why did Adobe open source Magento?
Why did Adobe open source Magento?
...despite the fact that, for example, Flash was proprietary and they, especially now, provide all their products by subscription?
They didn’t, the community edition existed before Adobes purchase.
Okay, but why then do they continue to support Magento (Community Edition) as open source?
The same reason a lot of companies support a community edition. It means that people can use, learn and become experienced with the product without forking over a tonne of money.
This results in a larger number of developers, add-ons and community surrounding the product.
This makes it a more appealing product for companies looking to build a business using it.
It's the same reason you can use AWS for free, get some JetBrains products for free and often find community editions for similar products to Magento.
why then do they continue
It was already open when they acquired it, so the question should rather be: why wouldn't they?
If they didn't want to do it, then they would not have acquired it in the first place.
Magento was open source before Adobe bought it, Flash wasn't.
"Why do Corpos allow People to work for free to improve their product?" - OP, evidently.