Are they European by any chance? EU law allows them to do that, the rest of us though are still bound by Humble's terms and conditions.

i believe trading links can be traced by their system

Hey,

Trader here. It is absolutely fine to trade games bought from Humble Bundle, but there are some rules.

1. Never, I repeat NEVER generate giftlinks and send them to traders. Use only activation keys. (XXXXX-XXXXX-XXXXX)
2. If you get a processing payment/purchases limit exceeded error on Humble Bundle, then it means that you account was marked. In that case, it is better to just abandon account and create a new one.
3. If you are trading your Humble Bundle games, then try to contact support as little as possible and never mention gifting/trading.
4. Unlink all accounts from HB account(Steam, Origin, Uplay..) as they are able to trace if bought game was activated on account or not.

I've never had a problem trading, and still trade gift links.
But I don't look to profit - I only buy bundles I care about, and trade away the leftovers.

just trade keys, not giftlinks and you gonna be fine , also don't buy bundles to resellers. Wherethe say they will give you like 15€ paypal ifyou buy a 10€ bundle