Earlier quoted context omitted.
It's also very possible they had been working on it already and wanted to compare notes, I certainly would if I were working on something internal and found a similar project, but I agree, ask them for a consultation fee. I don't see why they wouldn't pay it. Both projects also share in license, so I have less of an issue with it personally. They're both MIT licensed.
You are supposed to keep the original license for a fork. > The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. Simply removing the copyright is a violation of the MIT license.
It’s why con contributor licenses agreements exist in most open source popular projects.