What sphinx license is needed for a closed commercial system?

Question

Sphinx

Good afternoon.
We are engaged in the development of a complex closed system by order of an external organization, for internal use. Within the framework of the system, it is supposed to use a search engine. We wanted to use sphinx, but were puzzled by the license issue. Is it possible to use sphinx in such a system, or is it necessary to contact the authors and "purchase" a license? And in general, what types of licenses can be used for this product, without paying for the software used?

Answer 1

Everything is written here: sphinxsearch.com/services/embedding
Sphinx is distributed under the GPL. If for some reason this does not suit you (for example, you want to sell a product that sphinx will be part of, but not open your source code), then a commercial license can be purchased.