I believe OpenSky also doesn't censor their data, although in some areas I've looked at their coverage isn't quite as good as ADS-B Exchange. IIRC OpenSky is also a lot more permissive if you want to use their API
Unfortunately OpenSky does filter data (donors and sponsors to name a few) and is nothing more than a tax dollar black hole and front for commercially selling data while supporting the for profit Sero Systems.
ADSBx offered to share data, a data swap. Opensky was not interested and told us - "go fuck yourselves".
I know that there's a big financial incentive to censor aircraft data, and I haven't seen an explicit statement from OpenSky on their policies, so... I'm not sure.
