The license the project uses (AGPLv3) requires any server running a modified version of the software must include the source code. While it may not be possible to verify the source code running on someone else's server, you have the freedom to run the program on a server that you control. This ensures the version you are interacting with is not tampered with. Because the source code (and any modified code you can access on a network) are available, you or others can audit the code for security vulnerabilities.
This isn't a perfect solution because not everyone knows how to set up a server, but it definitely reduces the potential for abuse.
https://manual.consulproject.org/en/article/verify-your-acco...
the service can verify your identity relying on the city census. I wonder if you can identify yourself with a reader and your ID, which is mandatory and universal in Spain
https://firmaelectronica.gob.es/Home/en/Ciudadanos/DNI-Elect...