There are several places where it says "open source". It is ambiguous as "open source" doesn't necessarily mean it's free (as "free as a free speech").

Because Jamulus is distributed under a GNU GPL licence, it would then make sense that it should be at least "FOSS" (Free Open Source Software).

If we want to emphasise and disambiguate even further, we can use "FLOSS" or even "libre software" as written and suggested by Stallman on the FSF website.

@corrados : it would make sense for you to share your opinion here.