It is a minor adaptation of the Slax Linux distribution with my contribution being so small that you can check it for yourself and see that it does not contain malicious code. If you did the check, please post it here along with the checksums of the files inside your slax directory.

The file 9999-btcvault.sb contains all BTC Vault specific changes to Slax. Those changes are not many, so you can just unpack that module using the unsquashfs command and check the contents manually.