To get utxo data, Lighthouse used a p2p network bootstrapped via Mike Hearn's bitcoinXT software. I just use https://mempool.space which is a more centralized way to do it

Lighthouse assumed users keep funds in the built in wallet and then it marked some of them as "do not spend" if they were designated for a pledge. I just have users send the exact amount they want to contribute and don't assume users keep any additional funds in Semaphore

I use a multisig so that other people can't "complete" the fundraiser on the recipients behalf, he has to do it himself. I don't think Lighthouse did that, I think it allowed anyone who saw the published signatures to complete the transaction on the fundraiser's behalf

I have pledgers create 900 signatures in increments of 1% above the goal amount, that way the recipient can take the money even if he 10x's his goal. I don't think Lighthouse did that

I made a mechanism for semi automatic refunds using (again) presigned transactions, where a yone visiting the site 24 hours after the fundraiser ends automatically sends everyone their money back. I don't think Lighthouse had a similar feature

I also have an "irreversible pledge" option where you send the money directly to the recipient without doing any funky signature stuff, and I don't think Lighthouse had that