"Open source" is a vague description of a kind of license where the actual source code is made freely available provided that you meet certain conditions (ones other than "pay me some money"). To know exactly what you can and cannot do, you have to read the terms of the license. This license (CC-NC 4.0) disallows commercial use, whereas this license (CC-BY 4.0) allows commercial use. Before abandoning hope, you have to read the actual license, because CC-NC says that
NonCommercial means not primarily intended for or directed towards
commercial advantage or monetary compensation. For purposes of this
Public License, the exchange of the Licensed Material for other
material subject to Copyright and Similar Rights by digital
file-sharing or similar means is NonCommercial provided there is no
payment of monetary compensation in connection with the exchange.
Turns out that they mean "you can't re-sell this software", not "you can't use this software in your job, you can only use it for personal entertainment".
There are many licenses purporting to be "open", so you just have to read the license and see what the license says.