Daan is to give to any charity, while Dasvand it to given back to Guru Sahib for the propagation of Gurmat Naam.
Guru Sahib out of ritual cleansing, donations, and good deeds the highest deed accounted in Akal Purakhs court is Naam.
ਮਜਨੁ ਦਾਨੁ ਚੰਗਿਆਈਆ ਭਾਈ ਦਰਗਹ ਨਾਮੁ ਵਿਸੇਖੁ ॥
Daan and Daswandh are two separate things. Daan is something we give as charity and we get rewarded for that but Daswandh is not something we give because it was never ours to begin with. It belongs to Guru Sahib and is a property of Guru Khalsa Panth. It cannot be classified as Daan. Daan is given by a Daata (giver). Who are we to give Daan to Guru Sahib? We are beggars of Guru Sahib and have no standing to give Guru Sahib anything (except for our mind).
Daswandh is something that belongs to Guru Sahib to begin with and we do no charity when we give it. It belongs to Guru Sahib. We are merely temporary custodians of Daswandh. It’s true that sometimes in our texts, the term Daan has been used in place of Daswandh but still actual Daan is different from Daswandh. One is charity while the other one is not.
Some, out of ignorance, feel proud when the give Daswandh. They think that they are giving something in charity but nothing is farther from truth. Daswandh is the property of Guru Sahib and this is the reason it cannot be given to non-Sikh organizations and individuals. Guru’s wealth is used by Khalsa and that too for the betterment of Khalsa Panth and Gurmat as a whole. How can Daswandh be given to Salvation Army, Red Cross, Heart Foundation or other such good organizations that are run by Manmukhs? Yes, Manmukhs can receive benefit of Daswandh but through the channels of Khalsa Panth e.g. partaking Guru ka Langar, attending Sangat at Gurdwara Sahibaan that are pillars of Gurmat Parchaar, reading Gurmat Books etc.
Guru Sahib knows better.