This license is NOT open source, it only allows personal use, redistribution is prohibited, you can't modify or make update for other platforms, you can't modify and share your version, no community improvements, only works with ledger software.
Source-verifiable or software with
verifiable source code would then be the correct ways to explain Ledger Recovery Key. Under the condition, of course, that it is possible to reproduce it from the code available on GitHub. They seem to be using the same tricks that Coinkite and Coldcard were using in the past when they called their hardware wallets open-source for having publicly available code, but not meeting other conditions necessary to be open-source. They changed those claims to
source-verifiable eventually.