I've never heard of that before. I would think the ins would cover anyone injured on assn property, whether they're a member or not. But, if it is true, perhaps they could be required to sign a waiver. However, to be on the safe side, I would recommend checking with your ins. agent. 
 
Oftentimes renters are treated as "second-class" citizens, which I think is just terrible. I think they should be treated the same as the property owners with regard to being allowed to attend community events. After all,they do live in the community, right?

First, I think it's wonderful that your community offers social opportunities for members. Most don't.  
 
I would think it would be costly if you have a party that is paid for by the community but owners could invite guests. Some owners may be inclined to invite several frieds or family members to a party that would be a financial burden to owners.  
 
I did live in an active community that welcomed owner's family and friends. The owners were responsible for paying a fee for their guests to cover the basic cost. That prevented any negative reactions to guests and other owners made them feel welcome. 
 
This may be something you could suggest to your Board.

Renters should be carrying renters insurance that includes liability and an owner should be carrying additional insurance for liability and contents. I agree that you should read your condo association policy or contact the agent and the suggestion of a waiver is a good idea but may not be necessary.

No. No liability.