For me personally,
grassroots only has political connotations. But according to most dictionaries, it has 3 basic meanings.
1. basic, fundamental <the grassroots reason for purchasing land is ...>
2. totally new, not adapted from something else <a grassroots factory>
3. being, originating or operating in or at the basic foundation, source or lowest level of society or an organization. This is the meaning that I'm familiar with. <Obama has grassroots political support> <X is a grassroots movement> <X is a grassroots organization> All in a political context.