Each time a 2FA wallet user creates a transaction they are paying a small additional fee to this service (or rather every 20 transactions IIRC).
This is the first time that I heard about this, it is good that you mentioned it.
The fee are of two types, depending on how you want it:
0.000025 BTC/tx for 20 transactions which amounts to 0.0005 BTC in total
0.0000125 BTC/tx for 100 transactions which amounts to 0.00125 BTC total in total
It is on the FAQ of the link that you posted above:
https://trustedcoin.com/#/faq#feestrusted coin is a separate company. it's not owned by electrum. electrum does receive some of the 2fa wallet fees though. but it's not enough to cover their expenses.
Can we know more about how the fee is. I mean the percentage given to Electrum?
For donation, it would have been better if Electrum include a donation address to their website or on Electrum wallet. But Electrum developers do not want that.