It does matter a lot since it brings a solid foundation to build on, and that foundation is well tested, gets regular updates and makes it easy to create a super extensible application.

Most of users that look for such self hosted solution will know that using a framework is better than "pure php" because they get well tested code.

The use of a framework Does not mean the code is better, i would argue the opposite, many a new dev learns on a framework and often doesn't know the underlying language, whereas choosing not to use a framework is usually a conscious decision based on evaluation of actual needs.

I was talking only on my behalf :)

Since the product is self hosted and comes with the source code, if you want, you can customize it, fix bugs yourself, write custom features for clients, write extensions to sell, etc.

If it's built on a solid framework, and you study the framework, you'll know where to look when you want to change a model, a controller, so on.