You can use it in a commercial product, but if you distribute the commercial product it's going to require you to adhere to the GPL, which obviously has practical implications.

You can use it in an internal product that you use commercially, even if the program interacts with external users (e.g. web server) which is a big reason why AGPL exists.

Although, it's best to aware of what internal tools and software may require GPL distribution. For example it's the position of the FSF that distribution of internal tools to contractors requires adherence to the GPL.

https://www.gnu.org/licenses/gpl-faq.html#InternalDistributi...