One of them, called open-group-channel enables users to open a batch of balanced channels with many peers in a single transaction.
https://github.com/niteshbalusu11/BOS-Commands-Document#open-group-channel
Discussion
It uses Partially Signed Bitcoin Transactions (PSBT) under the hood, with one user (the initiator) creating the transaction and passing it around for each participating peer to provide their signature.
Once everybody has signed, the transaction is broadcast, resulting in multiple channels opening in a single Bitcoin transaction, which is both great for privacy (this is akin to a coinjoin) and an efficient use of blockspace (unlike JPEGs).
Last week, @HappyBear_Btc and @pfunzle, along with others, managed to open 6 channels in a single transaction using bos group open feature, which reportedly is the highest simultaneous open so far, [...]
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while the theoretical maximum is 420 peers (probably impossible to reach given the coordination challenges it presents).
This also made me think of an active discussion in the Bitcoin-Dev mailing list regarding an attack vector on multiparty protocols (such as Lightning or coinjoins, and even more opening Lightning channels in coinjoins) using Taproot inputs,
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2023-February/021444.html
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where the last party to sign can spend using a very big script path instead of the agreed upon key path, thus inflating the whole transaction's size and diminishing the overall feerate, as the absolute fee (in sats) was already committed to.
This attack doesn't steal funds per se, but degrades the expected "quality of service" (in terms of quick confirmation, for example), and can indirectly result in loss of funds in the case of time-sensitive protocols. Definitely something to keep in mind!