what is ToS
ToS means "Terms of Service"
You can read the ToS here
Basically they don't want the following: (well my take of it anyway)
7. User Conduct
(a) Upload, post, email, transmit or otherwise make available any Submission (as defined below) that is unlawful, harmful, threatening, abusive, harassing, tortuous, defamatory, vulgar, obscene, libelous, invasive of another's privacy, hateful, or racially, ethnically or otherwise objectionable;