Any commercial enterprise can use Open Source Software with a share, commercial, and editable license commercially. You'd have to look at the specific licenses, but usually open source software allows commercial use.
Legal Advice
The MIT license allows for commercial use, but I'm wondering about this clause in the MIT license:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
Doesn't that mean the MIT license must be shown somewhere?
(the BSD and Apache 2.0 license have something similar too)
They only have to include that if they actually send you the software (depending on license, either when they send you binaries, source code, or both). Interacting with the server over the internet doesn’t count, unless they’re sending the browser JavaScript covered by such a license.
There are a few licenses that explicitly demand this sort of thing when you run the software on your own servers but let other people communicate with the software over the network, but none of the big name, long-standing licenses like MIT, BSD, Apache or GPL have that requirement.
unless they’re sending the browser JavaScript covered by such a license.
I think the claim here is that they are.
It would seem to indicate that, and perhaps Reddit does have it, buried in a long document somewhere.
Note that I am not a lawyer, and this is not legal advice.