I am unaware of anything about Startpage that is Free Software. A good portion of DuckDuckGo is Open Source. It seems very clear that their reason for doing such is around security and allowing users to verify such.The "core" of their search engine, which I understand to include the actual search algorithm, however, remains proprietary. SearXNG is primarily focused on users who want to make the service available to the general public through hosting instances available via the www, similar to how Mastodon and other fediverse platforms work, it has slightly fewer privacy controls than SearX to make it easier to use for the general public. A list of currently available public instances can be found at https://searx.space/. As a fork of SearX it is also published under the AGPL. As SearXNG is a metasearch engine, not all of the tools it utilizes to make searches are Free Software, however it has built into it the ability toggle on/off which search engines it references for your p