Without checking for compatibility between the licenses -- if they are both open source, it is possible to combine the best of both tools.
That's actually why I built GnuCash-Helper[0]. It's a web-based personal finance tool written with Python and Flask that works with GnuCash files. It's not nearly ready for prime time, but I use it daily, and I don't even open GnuCash anymore.
In general, I really wish that GnuCash would get a visual refresh and some more modern features. It's amazing, but it looks very 2006, and it has bad stories for mobile and web. Obviously, HN readers are a different breed, but good luck convincing most people to run desktop-only software in 2023.
I was asked by someone to help them find a desktop-only invoicing app because they didn't have reliable internet at their place of business. Sure, most people will want web apps, but there are always subpopulations with specific requirements that one can target.